Multifunctional repellent materials

ABSTRACT

Methods and compositions disclosed herein relate to liquid repellant surfaces having selective wetting and transport properties. An article having a repellant surface includes a substrate comprising fabric material and a lubricant wetting and adhering to the fabric material to form a stabilized liquid overlayer, wherein the stabilized liquid overlayer covers the fabric material at a thickness sufficient to form a liquid upper surface above the fabric material, wherein the fabric material is chemically functionalized to enhance chemical affinity with the lubricant such that the lubricant is substantially immobilized on the fabric material to form a repellant surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims the benefit of the earlier filing date of U.S.Patent Application No. 61/671,442, filed on Jul. 13, 2012; U.S. PatentApplication No. 61/671,645, filed on Jul. 13, 2012; and U.S. PatentApplication No. 61/673,705, filed on Jul. 19, 2012, the contents ofwhich are incorporated by reference herein in their entireties.

The present application related to the following co-pending applicationsfiled on even date herewith:

International Application entitled SELECTIVE WETTING AND TRANSPORTSURFACES, filed on even date herewith;

International Application entitled SLIPS SURFACE BASED ONMETAL-CONTAINING COMPOUND, filed on even date herewith:

International Application entitled MULTIFUNCTIONAL REPELLENT MATERIALS,filed on even date herewith;

the contents of which are incorporated by reference herein in theirentireties.

STATEMENT CONCERNING GOVERNMENT RIGHTS IN FEDERALLY-SPONSORED RESEARCH

This invention was made with government support underFA9550-09-1-0669-DOD35CAP awarded by the U.S. Air Force and underDE-AR0000326 awarded by the U.S. Department of Energy. The governmenthas certain rights in the invention.

TECHNICAL FIELD

The field of this application generally relates to slippery surfaces,methods for forming them, and their uses.

BACKGROUND

Current development of liquid-repellent surfaces is inspired by theself-cleaning abilities of many natural surfaces on animals, insects,and plants. Water droplets on these natural surfaces roll off or slideoff easily, carrying the dirt or insects away with them. The presence ofthe micro/nanostructures on many of these natural surfaces has beenattributed to the water-repellency function. These observations have ledto enormous interests in manufacturing biomimetic water-repellentsurfaces in the past decade, owing to their broad spectrum of potentialapplications, ranging from water-repellent fabrics to friction-reductionsurfaces.

SUMMARY

Liquid repellant surfaces having selective wetting and transportproperties and their applications in a variety of fields are described.In certain embodiments, such liquid repellant surfaces have additionalfunctionalities, in addition to the wetting and transport properties.

Disclosed subject matter includes, in one aspect, an article having arepellant surface, which includes a substrate comprising fabric materialhaving a weave density that is greater than 100 threads/cm² and alubricant wetting and adhering to the fabric material to form astabilized liquid overlayer, wherein the stabilized liquid overlayercovers the fabric material at a thickness sufficient to form a liquidupper surface above the fabric material, wherein the fabric material ischemically functionalized to enhance chemical affinity with thelubricant such that the lubricant is substantially immobilized over thefabric material to form a repellant surface.

Disclosed subject matter includes, in another aspect, an optical articlehaving a repellant surface, which includes a substrate comprisingtransparent or translucent material with a surface, a housing that holdsthe substrate, and a lubricant wetting and adhering to the surface toform a stabilized liquid overlayer, wherein the stabilized liquidoverlayer covers the surface at a thickness sufficient to form a liquidupper surface above the surface, wherein the surface and the lubricanthave an affinity for each other such that the lubricant is substantiallyimmobilized on the substrate to form a repellant surface, wherein thehousing is infiltrated with the lubricant to replenish the lubricantonto the substrate.

Disclosed subject matter includes, in another aspect, an article havinga repellant inner surface, which includes a container comprising aninner surface to contain a complex fluid; and a complex fluid having aliquid and one or more other components within said container; whereinthe liquid wets and adheres to the inner surface to form a stabilizedliquid overlayer, wherein the stabilized liquid overlayer covers theinner surface at a thickness sufficient to form a liquid surface on theinner surface, wherein the inner surface and the liquid have an affinitysuch that the liquid is substantially immobilized on the inner substrateto form a repellant surface, the repellant surface repelling othercomponents within said complex fluid.

Disclosed subject matter includes, in another aspect, a membrane-likearticle, which includes a membrane substrate comprising a top surface, abottom surface, and a plurality of through-holes and a low-surfacetension fluid wetting and adhering the top surface, the bottom surface,and inner walls surrounding the plurality of through-holes, forming apre-conditioning layer and a fluid deposited over the pre-conditioninglayer to form a protective layer, the protective laying providing arepellant surface to the membrane substrate, wherein the membranesubstrate, the pre-conditioning layer, and the protective layer have anaffinity to each other such that the protective layer is substantiallyimmobilized on the membrane substrate to form the repellant surface.

Disclosed subject matter includes, in another aspect, an article forcarrying fluid flow, which includes a substrate comprising a roughenedsurface and a lubricant wetting and adhering to the roughened surface toform a stabilized liquid overlayer, wherein the stabilized liquidoverlayer covers the roughened surface at a thickness sufficient to forma liquid upper surface on top of the roughened surface, wherein theroughened surface and the lubricant have an affinity for each other suchthat the lubricant is substantially immobilized on the substrate to forma slippery surface, the slippery surface reducing drag and friction ofthe fluid flow.

Disclosed subject matter includes, in another aspect, a method forprotecting metal or metalized surfaces from corrosion, which includesproviding a metal or metalized surface, introducing roughness, andchemically functionalizing the metal or metalized surface to enhanceaffinity of the metal surface with a lubricant and introducing thelubricant to wet and adhere to the metal or metalized surface to form anoverlayer, wherein the metal or metalized surface and the lubricant havean affinity for each other such that the lubricant is substantiallyimmobilized on the substrate to form a repellant surface, providinganti-corrosion to the metal or metalized surface.

Disclosed subject matter includes, in another aspect, a method forprotecting surfaces from scaling, which includes providing a surface,introducing roughness, and chemically functionalizing the surface toenhance affinity of the surface with a lubricant, and introducing thelubricant to wet and adhere to the surface to form an overlayer, whereinthe surface and the lubricant have an affinity for each other such thatthe lubricant is substantially immobilized on the substrate to form arepellant surface, providing anti-scaling to the metal surface.

Disclosed subject matter includes, in another aspect, an article havinga repellant surface, which includes a substrate comprising a roughenedsurface; a lubricant wetting and adhering to the roughened surface toform a stabilized liquid overlayer, wherein the liquid covers theroughened surface at a thickness sufficient to form a liquid uppersurface above the roughened surface; and a fragrance enhancer locatedwithin said substrate and/or said lubricant; wherein the roughenedsurface and the lubricating liquid have an affinity for each other suchthat the lubricating liquid is substantially immobilized on thesubstrate to form a repellant surface.

In certain embodiments, the roughened surface and/or the liquid possessmore than one chemical state that can be switched to enhance or diminishthe affinity between the surface and the lubricating liquid.

Disclosed subject matter includes, in another aspect, an article havinga repellant surface, which includes a substrate comprising a roughenedsurface and a lubricant wetting and adhering to the roughened surface toform a stabilized liquid overlayer, wherein the liquid covers theroughened surface at a thickness sufficient to form a liquid uppersurface above the roughened surface, wherein the roughened surface andthe lubricating liquid have an affinity for each other such that thelubricating liquid is substantially immobilized on the substrate to forma repellant surface, wherein the roughened surface includes a microscaleor nanoscale structure.

In certain embodiments, the substrate includes a plurality of nanofibersor nanotubes embedded in an epoxy medium.

Disclosed subject matter includes, in another aspect, an article havinga repellant surface, which includes a substrate comprising an at leastpartially roughened surface and a lubricant wetting and adhering to theroughened surface to form a kinetically stabilized liquid overlayer,wherein the liquid covers the roughened surface at a thicknesssufficient to form a liquid upper surface above the roughened surface,wherein the roughened surface or parts of the roughened surface and thelubricating liquid have an affinity for each other such that thelubricating liquid is substantially immobilized on the substrate to forma repellant surface. The meta-stability prevents thermodynamicallyfavorable displacement of the liquid for at least a certain amount oftime.

Disclosed subject matter includes, in another aspect, a method forvapors collection, which includes providing a solid surface, introducingroughness, chemically functionalizing the solid surface to enhanceaffinity of the surface with a lubricant, introducing the lubricant towet and adhere to the solid surface to form an overlayer, wherein thesolid surface and the lubricant have an affinity for each other suchthat the lubricant is substantially immobilized on the substrate to forma repellant surface, and condensing condensate droplets on the repellantsurface for liquid collection.

Disclosed subject matter includes, in another aspect, an article havinga repellant surface, which includes a substrate comprising a roughenedsurface and a lubricant wetting and adhering to the roughened surface toform a stabilized liquid overlayer, wherein the liquid covers theroughened surface at a thickness sufficient to form a liquid uppersurface above the roughened surface, wherein the roughened surface andthe lubricating liquid have an affinity for each other such that thelubricating liquid is substantially immobilized on the substrate to forma repellant surface, wherein the substrate is a component of a ski, aluge, a surf board, a hovercraft, a winter sports item, or a watersports item.

Disclosed subject matter includes, in another aspect, a method forprotecting plastic, glass, ceramic, and composite surfaces from scaling,which includes providing a said solid surface, introducing roughness,chemically functionalizing the said surface to enhance affinity of thesaid surface with a lubricant, and introducing the lubricant to wet andadhere to the said surface to form an overlayer, wherein the surface andthe lubricant have an affinity for each other such that the lubricant issubstantially immobilized on the substrate to form a repellant surface,providing anti-scaling to the said surface.

Disclosed subject matter includes, in another aspect, a method forprotecting plastic, glass, ceramic, and composite surfaces fromgraffiti, which includes providing a said solid surface, introducingroughness, chemically functionalizing the said surface to enhanceaffinity of the said surface with a lubricant, and introducing thelubricant to wet and adhere to the said surface to form an overlayer,wherein the said surface and the lubricant have an affinity for eachother such that the lubricant is substantially immobilized on thesubstrate to form a repellant surface, providing anti-graffitiproperties to the said surface.

Disclosed subject matter includes, in another aspect, method for forminga repellent surface, which includes providing a substrate having asurface, depositing a first material having a charge to said surface;depositing a second material having a charge that is opposite to thecharge of the first material; sequentially repeating said depositing afirst material and said depositing a second material to provide aroughened surface; and introducing a lubricant to wet and adhere to saidroughened surface to form an overlayer, wherein said roughened surfaceand said lubricant have an affinity for each other such that thelubricant is substantially immobilized on the substrate to form arepellent surface.

Disclosed subject matter includes, in another aspect, a method to reducefriction against fluids and solids, which includes providing a saidsolid surface, introducing roughness, chemically functionalizing thesaid surface to enhance affinity of the said surface with a lubricant,and introducing the lubricant to wet and adhere to the said surface toform an overlayer, wherein the said surface and the lubricant have anaffinity for each other such that the lubricant is substantiallyimmobilized on the substrate to form a repellant surface, providinganti-graffiti properties to the said surface.

Disclosed subject matter includes, in another aspect, a method to reduceadhesion against fluids and solids, which includes providing a saidsolid surface, introducing roughness, chemically functionalizing thesaid surface to enhance affinity of the said surface with a lubricant,and introducing the lubricant to wet and adhere to the said surface toform an overlayer, wherein the said surface and the lubricant have anaffinity for each other such that the lubricant is substantiallyimmobilized on the substrate to form a repellant surface, providinganti-graffiti properties to the said surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are provided for the purpose of illustration onlyand are not intended to be limiting.

FIG. 1 shows a schematic of a self-healing slippery liquid-infusedporous surface (SLIPS) in accordance with certain embodiments of thepresent disclosure:

FIG. 2 illustrates a general scheme of creating SLIPS in accordance withcertain embodiments of the present disclosure;

FIGS. 3A-3B illustrates the comparison between a thermodynamicallystable SLIPS with a kinetically stable (meta-stable) SLIPS) inaccordance with certain embodiments of the present disclosure;

FIG. 3C further illustrates an exemplary meta-stable SLIPS state;

FIG. 4A-4B shows the wetting behaviors of an exemplary fluorinatedliquid B on (A) a flat surface and (B) nanostructured surface;

FIG. 5A shows a schematic of an exemplary columnar porous material overwhich the slippery surface is formed;

FIG. 5B shows a schematic of an exemplary inverse opal porous materialover which the slippery surface is formed;

FIG. 5C shows an image of an exemplary random network porous materialover which the slippery surface is formed;

FIG. 5D shows an image of exemplary self-assembled polymericmicrostructures induced by solvent drying in accordance with certainembodiments of the present disclosure;

FIG. 5E shows a schematic of an exemplary structured surface over whichthe slippery surface is formed;

FIG. 6 shows a replication process to reproduce the morphology of theSLIPS surface, where the corresponding surface characterizationindicates ultra-smoothness of the SLIPS, in accordance with certainembodiments;

FIG. 7A shows images of SLIPS demonstrating self-healing properties,where the self-healing time scale is on the order of 100 ms, inaccordance with certain embodiments;

FIG. 7B is a chart showing restoration of liquid repellency functionafter critical physical damages (Test liquid=decane, γ_(LV)=23.6±0.1mN/m) in accordance with certain embodiments;

FIG. 7C shows time-lapse images demonstrating the restoration of liquidrepellency of a SLIPS after physical damage, as compared to a typicalhydrophobic flat surface on which oil remains pinned at the damage site,in accordance with certain embodiments;

FIG. 7D illustrates a self-refilling mechanism in accordance withcertain embodiments;

FIGS. 8, 9A-9C show some exemplary common natural and synthetic fabricssystems.

FIGS. 10A-10C demonstrates SLIPS fabrics for functional clothing againstvarious complex fluids and high temperature fluids in accordance withcertain embodiments;

FIG. 11 demonstrates photographs of a fog test on a 60 C water.

FIG. 12 shows a schematic illustration of a fog-free optical viewingcover for microscope.

FIG. 13 contains a schematic illustration of a circular optics encasedin a lubricant-containing O-ring serving as a reservoir in accordancewith certain embodiments.

FIG. 14 demonstrates a photograph of camera lens protectors inaccordance with certain embodiments.

FIG. 15 further demonstrates a photograph of anti-reflective camera lensprotectors in accordance with certain embodiments.

FIG. 16A shows a regulatory approval chart of various materials.

FIGS. 16B and 16C illustrate SLIPS-treated bottles and containersrepelling complex food products, such as ketchup, mayonnaise, andoatmeal, in accordance with certain embodiments.

FIG. 16D illustrates SLIPS-treated ice tray repelling ice, in accordancewith certain embodiments.

FIG. 17 is a schematic showing different methods to produce slipperysurfaces using fragrance/flavor-enhanced lubricants in accordance withcertain embodiments.

FIG. 18 illustrates pressure drop on internally coated pipe as afunction of flow in accordance with certain embodiments.

FIG. 19 illustrates the time lapse of untreated Al (left) andSLIPS-coated Al (right) immersed in 1 M KOH solution at room temperatureshowing rapid degradation of untreated aluminum while coated Alessentially remains unchanged.

FIG. 20 shows the steps involved in the nucleation, coalescence andsliding of water droplets on a conventional hydrophobic surface and aSLIPS in accordance with certain embodiments.

FIGS. 21 and 22 show SLIPS-treated surfaces that can function asanti-graffiti surfaces in accordance with certain embodiments.

FIG. 23A shows a schematic illustration of the layer-by-layer depositionprocess to form porous, lubricant-infused coatings in accordance withcertain embodiments.

FIG. 23B shows SEM images of the silica coating show the increase indeposited particles with increasing coating cycles in accordance withcertain embodiments.

FIG. 24A shows a plot demonstrating the increase in deposited mass foreach consecutive layer-by-layer adsorption cycle, calculated usingSauerbrey's equation from the frequency drop measured by Quartz CrystalMicrobalance in accordance with certain embodiments.

FIG. 24B shows a plot of number of silica nanoparticles deposited ontothe substrate during each adsorption cycle (gray) and as cumulativeduring the complete process (black line) calculated from QCM-D data. Anear-linear increase in deposited particles with increasing coatingcycles is visible in accordance with certain embodiments.

FIG. 24C shows UV-Vis-NIR transmittance spectra of lubricated samplesafter calcination and fluorosilanization of the silica nanoparticlecoating. With increasing numbers of deposited layers, an increase inlight transmittance is observed for all coatings as compared to a normalglass slide in accordance with certain embodiments.

FIGS. 25A and 25B show repellency of a 10 μl droplet of water (a) andoctane (b) in dry and lubricated state for coatings with up to 9deposited layers. The lubricated samples drastically outperform bothuncoated (0 layers) and dry, coated substrates and feature extremelysmall sliding angles for both liquids in accordance with certainembodiments.

FIGS. 25C and 25D show time-lapse pictures of a water (c) and octane (d)droplet sliding under an angle of 2° on a lubricated substrate with 5deposited silica nanoparticle layers without getting pinned to thesubstrate in accordance with certain embodiments.

FIGS. 26A through 26D compares time-lapsed images taken from foruntreated (upper row) and lubricated layer-by-layer assembled SiO₂nanoparticle coated surfaces (lower row) using a) honey in the inside ofa glass vial, b) crude oil in a glass tube; c) octane sliding down astainless steel surface; d) octane sliding down a polymethylmethacrylate surface in accordance with certain embodiments.

FIGS. 27A through 27D shows contact angle hysteresis and sliding anglesfor water and hexadecane for SLIPS formed over PDMS substrate using alayer-by-layer assembly approach in accordance with certain embodiments.

FIG. 28 shows sliding angles as a function of applied strain inaccordance with certain embodiments.

FIGS. 29A-29D show SEM images of a porous “paper” produced from boehmitenanofibers in accordance with certain embodiments.

FIG. 29E shows a TEM image of individual solvothermal boehmitenanofibers with some agglomerated particles in accordance with certainembodiments.

FIG. 29F shows SEM image of bundled boehmite nanofibers drop cast on acopper conductive tape in accordance with certain embodiments.

FIGS. 30A and 30B show a (A) top view and (B) cross section HR-SEMimages of multi wall carbon nanotubes dispersed in epoxy resin matrixprior plasma etching in accordance with certain embodiments.

FIG. 31A shows an exemplary method to generate surface functionalizedalumina nanoparticles (AlNPs) for use as filler material innanocomposites in accordance with certain embodiments.

FIG. 31B shows the normalized FTIR absorbance spectra of O—H stretchingmode recorded from AlNPs taken at different treatment times with Fentonchemistry in accordance with certain embodiments.

FIG. 32 shows a schematic design principles of lubricated nanostructuredfabrics (SLIPS-fabrics) in accordance with certain embodiments.

FIG. 33 shows SEM images of the weave pattern of different fabrics inaccordance with certain embodiments.

FIG. 34 shows SEM images of the fabrics after various differenttreatments in accordance with certain embodiments.

FIG. 35A shows static contact angle data for all the differentfunctionalized fabrics in accordance with certain embodiments.

FIG. 35B shows contact angle hysteresis data for all the differentfunctionalized fabrics in accordance with certain embodiments.

FIG. 36 shows twisting test results to determine robustness for a set offunctionalized fabrics in accordance with certain embodiments.

FIG. 37 shows drop impact characterization of SLIPS-treated fabrics inaccordance with certain embodiments.

DETAILED DESCRIPTION

The patent and scientific literature referred to herein establishesknowledge that is available to those of skill in the art. The issuedU.S. patents, allowed applications, published foreign applications, andreferences, that are cited herein are hereby incorporated by referenceto the same extent as if each was specifically and individuallyindicated to be incorporated by reference.

For convenience, certain terms employed in the specification, examplesand claims are collected here. Unless defined otherwise, all technicaland scientific terms used in this disclosure have the same meanings ascommonly understood by one of ordinary skill in the art to which thisdisclosure belongs. The initial definition provided for a group or termprovided in this disclosure applies to that group or term throughout thepresent disclosure individually or as part of another group, unlessotherwise indicated.

The present disclosure describes slippery surfaces referred to herein asSlippery Liquid-Infused Porous Surfaces (SLIPS). In certain embodiments,the slippery surfaces of the present disclosure exhibitsubstance-repellent, drag-reducing, anti-adhesive and anti-foulingproperties. The slippery surfaces of the present disclosure are able toprevent adhesion of a wide range of materials. Exemplary materials thatdo not stick onto the surface include liquids, solids, and gases (orvapors). For example, liquids such as water, oil-based paints,hydrocarbons and their mixtures, organic solvents, complex fluids suchas crude oil, fluids containing complex biological molecules (such asproteins, sugars, lipids, etc) and biological cells and the like can berepelled. The liquids can be both pure liquids and complex fluids. Incertain embodiments, SLIPS can be designed to be omniphobic, where SLIPSexhibit both hydrophobic and oleophobic properties. As another example,solids such as bacteria, insects, fungi and the like can be repelled oreasily cleaned. As another example, solids such as ice, paper, stickynotes, or inorganic particle-containing paints, dust particles can berepelled or cleaned. SLIPS surfaces are discussed in InternationalPatent Application Nos. PCT/US2012/21928 and PCT/US2012/21929, bothfiled Jan. 19, 2012, and U.S. Provisional Patent Applications 61/671,442and 61/671,645, both filed Jul. 13, 2012, the contents of which arehereby incorporated by reference in their entireties.

Such materials that can be prevented from sticking to the slipperysurfaces disclosed herein are referred to herein as “Object A.” Object Athat is in liquid form is referred to as “Object A in liquid form,” or“liquefied Object A,” or “Liquid A.” Object A that is in solid form isreferred to as “Object A in solidified form,” or “solidified Object A”or “Solid A.” Object A that is in gaseous/vapor form is referred to as“Object A in gaseous form”, or “gaseous Object A”. In certainembodiments, Object A can contain a mixture of both solids and fluids(i.e., gas/vapor/liquid mixed with a solid; eg particles in air, orparticles in liquids). In certain embodiments, Object A can contain amixture of both gas/vapors and liquids.

A wide range of materials can be repelled by the slippery surfaces ofthe present disclosure. For example, Object A can include polar andnon-polar Liquids A, their mixtures, and their solidified forms, such ashydrocarbons and their mixtures (e.g., from pentane up to hexadecane andmineral oil, paraffinic extra light crude oil; paraffinic light crudeoil; paraffinic light-medium crude oil; paraffinic-naphthenic mediumcrude oil; naphthenic medium-heavy crude oil; aromatic-intermediatemedium-heavy crude oil; aromatic-naphthenic heavy crude oil,aromatic-asphaltic crude oil, etc.), ketones (e.g., acetone, etc.),alcohols (e.g., methanol, ethanol, isopropanol, higher alcohols,propylene glycol, dipropylene glycol, ethylene glycol, and glycerol,etc.), water (with a broad range of salinity, e.g., containing sodiumchloride or bromide from 0 to 6.1 M; potassium chloride or bromide from0 to 4.6 M, water with high affinity to scaling, such as having highconcentration of Mg and Ca ions, etc.), acids (e.g., concentratedhydrofluoric acid, hydrochloric acid, nitric acid, etc) and bases (e.g.,potassium hydroxide, sodium hydroxide, etc), and ice, etc. Object A caninclude biological objects, such as insects, small animals, protozoa,bacteria, viruses, fungi, bodily fluids and fecal matter, tissues,biological molecules (such as proteins, sugars, lipids, etc.), and thelike. Object A can include gasses, such as natural gas, air or watervapors. Object A can include solid particles suspended in liquid. ObjectA can include solid particles suspended in gas. Object A can includenon-biological objects, such as dust, colloidal suspensions, spraypaints, food items, common household materials, and the like. Object Acan include adhesives and adhesive films. The list is intended to beexemplary and the slippery surfaces of the present disclosure areenvisioned to successfully repel numerous other types of materials andmaterials combinations.

In certain embodiments, the slippery surface of the present disclosurehas a coefficient of friction that is lower than that ofpolytetrafluoroethylene (PTFE or Teflon™) surface. In certainembodiments, the coefficient of friction may be less than 0.1, less than0.05, or even less than 0.04. In certain embodiments, the coefficient offriction can be measured by sliding two different surfaces against eachother. The value of the coefficient of friction should beload-independent. The friction force can depend on the load applied ontothe surface, the sliding velocity, and the materials of the surfaces.For example, a reference surface, such as a polished steel, could beused to slide against the target surfaces, such as Teflon, or the SLIPSof the present disclosure could be used to slide against itself (e.g.,SLIPS/SLIPS) to obtain the coefficients of friction (both static anddynamic).

A schematic of the overall design of Slippery Liquid-Infused PorousSurfaces (SLIPS) is illustrated in FIG. 1. As shown, the articleincludes a solid surface 100 having surface features 110 that provide acertain roughness (i.e. roughened surface) with Liquid B 120 appliedthereon. Liquid B wets the roughened surface, filling the hills,valleys, and/or pores of the roughened surface, and forming anultra-smooth surface 130 over the roughened surface. Due to theultra-smooth surface resulting from wetting the roughened surface withLiquid B and forming a flat liquid overlayer, Object A 140 does notadhere to the surface.

In certain embodiments, the surface features 110 can be functionalizedwith one or more functional moieties 150 that further promote adhesionof the Liquid B 120 to the surface features 110. In certain embodiments,the functional moieties 150 can resemble the chemical nature of Liquid B120. In certain embodiments, the surface features 110 can befunctionalized with one or more functional moieties 150 that arehydrophobic.

In some embodiments, the Liquid B follows the topography of theroughened surface (e.g., instead of forming a smooth layer thatovercoats all the textures). For example, Liquid B may follow thetopography of the roughened surface if the equilibrium thickness of theoverlayer is less than the height of the textures.

SLIPS can be designed based on the surface energy matching between alubricating fluid and a solid (i.e. formation of a stable lubricatingfilm which is not readily displaced by other, immiscible fluids). Insome embodiments, SLIPS can be designed based on at least the followingthree factors: 1) the lubricating liquid (Liquid B) can infuse into,wet, and stably adhere within the roughened surface, 2) the roughenedsurface can be preferentially wetted by the lubricating liquid (LiquidB) rather than by the Object A, complex fluids or undesirable solids tobe repelled (Object A), and 3) the lubricating fluid (Liquid B) and theobject or liquid to be repelled (Object A) can be immiscible and may notchemically interact with each other. These factors can be designed to bepermanent or lasting for time periods sufficient for a desired life orservice time of the SLIPS surface or for the time till a reapplicationof the partially depleted infusing liquid is performed.

The first factor (a lubricating liquid (Liquid B) which can infuse into,wet, and stably adhere within the roughened surface) can be satisfied byusing micro- and/or nanotextured, rough substrates whose large surfacearea, combined with chemical affinity for Liquid B, facilitates completewetting by, and adhesion of, the lubricating fluid. More specifically,the roughness of the roughened surface, R, can be selected such thatR≧1/cos θ_(BX), where R is defined as the ratio between the actual andprojected areas of the surface, and θ_(BX) is the equilibrium contactangle of Liquid B on a flat solid substrate immersed under medium X(X=water/air/other immiscible fluid medium). R factor can vary between 1and infinity. In certain embodiments, R may be any value greater than orequal to 1, such as 1 (flat, smooth surface), 1.5, 2, 5, or even higher.

The stable adhesion of the liquid B to the underlying solid is oftenachieved through chemical functionalization or applications of a coatingthat has a very high affinity to both Liquid B and the solid, thusproducing a stable chemical or physical bonding between the liquid B andthe solid.

To satisfy the second factor (that the roughened surface can bepreferentially wetted by the lubricating liquid (Liquid B) rather thanby the liquid, complex fluids or undesirable solids to be repelled(Object A)), a determination of the chemical and physical propertiesrequired for working combinations of substrates and lubricants can bemade. This relationship can be qualitatively described in terms ofaffinity; to ensure that the Object A to be repelled (fluid or solid)remains on top of a stable lubricating film of the lubricating liquid,the lubricating liquid must have a higher affinity for the substratesurface than materials to be repelled, such that the lubricating layercannot be displaced by the liquid or solid to be repelled. Thisrelationship can be described as a “stable” region. As stated above,these relationships for a “stable” region can be designed to besatisfied permanently or for a desired period of time, such as lifetime,service time, or for the time till the replenishment/reapplication ofthe partially depleted infusing liquid is performed. In order to createa stable (or energetically favorable) Liquid B-solid interface, thefollowing condition has to be satisfied:

ΔE ₀=γ_(AS)−γ_(BS)=γ_(BX) cos θ_(RB)−γ_(AX) cos θ_(AX)>0  (eq. 0)

where γ_(AS) and γ_(BS) are the interfacial tension of solid-liquid Aand solid-liquid B interfaces respectively; γ_(BX) and γ_(AX) are theinterfacial tension of lubricating fluid (Liquid B) and other immisciblefluid (Liquid A) with medium X; θ_(BX) and θ_(AX) are the contact angleof Liquid B and Liquid A on the solid under medium X, where X can be airor other immiscible phases with the solid, Liquid A, and Liquid B. Thecondition includes both kinetically stable and thermodynamically stableSLIPS. Also, see FIGS. 3A and 3B.

Kinetically-stable SLIPS will form for certain combinations that do notsatisfy eq. 0, where either (i) the Liquid B-solid interface may begradually replaced by that of the Liquid A-solid interface over time, t,if Liquid A has a higher affinity to the solid surface than Liquid B (inother words, if an additional energy penalty is required to form LiquidB-Liquid A interface); or (ii) if Liquid A and B show some reactivity ormiscibility over time degrading the slippery interface quality. Thesekinetically stable SLIPS would still show improved performance overexisting surfaces, if the SLIPS need to keep their properties onlywithin a limited period of time.

In order to create a stable (or energetically/thermodynamicallyfavorable) SLIPS materials that are not degraded over time and whereLiquid B is not being replaced by an Object A, the following criteriamust be satisfied. A comparison of the total interfacial energiesbetween textured solids that are completely wetted by either anarbitrary immiscible liquid (E_(A)), or a lubricating fluid with (E₁) orwithout (E₂) a fully wetted immiscible test liquid floating on top of itcan be calculated. This can ensure that Object A remains on top of astable lubricating film of Liquid B. In order to ensure that the solidis wetted preferentially by the lubricating fluid, both ΔE₁=E_(A)−E₁>0and ΔE₂=E_(A)−E₂>0 should be true. The equations can be expressed as:

ΔE ₁ =R(γ_(BX) cos θ_(BX)−γ_(AX) cos θ_(AX))−γ_(AB)>0  (eq. 1)

ΔE ₂ =R(γ_(BX) cos θ_(BX)−γ_(AX) cos θ_(AX))+γ_(AX)−γ_(BX)>0  (eq. 2)

where R is the roughness factor (i.e. the ratio between the actual andprojected surface areas of the textured solids).

This relationship can also be qualitatively described in terms ofaffinity; to ensure that Object A remains on top of a stable lubricatingfilm of Liquid B, Liquid B must have a higher affinity for the substratethan Object A. For example, a solid functionalized or coated withhydrophilic molecules and infiltrated with polar Liquids B, will providea functional oleophobic SLIPS for repelling oils; a solid functionalizedor coated with hydrophobic moieties and infiltrated with hydrocarbons asLiquid B will provide a functional hydrophobic surface for repellingpolar, hydrophilic materials, such as water; a solid functionalized orcoated with fluorinated molecules and infiltrated with fluorinated oilswill work as functional SLIPS that are both hydrophobic and oleophobic;etc. For patterned SLIPS, this relationship can be described as a“stable” region. Conversely, where Object A has a higher affinity forthe substrate (for example, an unfunctionalized region of the substrate)than Liquid B, Object A will displace Liquid B in that region. Thisrelationship can be described as an “unstable” region.

To satisfy the third factor (that the lubricating fluid (Liquid B) andthe object or liquid to be repelled (Object A) can be immiscible and maynot chemically interact with each other), the enthalpy of mixing betweenObject A and Liquid B should be sufficiently high (e.g., water/oil;insect/oil; ice/oil, etc.) that they phase separate from each other whenmixed together, and/or do not undergo substantial chemical reactionsbetween each other. In certain embodiments, Object A and Liquid B aresubstantially chemically inert with each other so that they physicallyremain distinct phases/materials without substantial mixing between thetwo. For excellent immiscibility between Liquid A and Liquid B, thesolubility in either phase should be <500 parts per million by weight(ppmw). For example, the solubility of water (Liquid A) inperfluorinated fluid (Liquid B, e.g., 3M Fluorinert™) is on the order of10 ppmw; the solubility of water (Liquid A) in polydimethylsiloxane(Liquid B, MW=1200) is on the order of 1 ppm. In some cases. SLIPSperformance could be maintained transiently with sparingly immiscibleLiquid A and Liquid B. In this case, the solubility of the liquids ineither phase is <500 parts per thousand by weight (ppthw). Forsolubility of >500 ppthw, the liquids are said to be miscible. Forcertain embodiments, an advantage can be taken of sufficiently slowmiscibility or mutual reactivity between the infusing liquid and theliquids or solids or objects to be repelled, leading to a satisfactoryperformance of the resulting SLIPS over a desired period of time.

In some embodiments, a spatially heterogeneous pattern on aliquid-coated surface is created by first functionalizing a solidsurface with spatially defined surface energy. When a given lubricant iswetted on a solid surface, the surface can be designed such that part ofthe region can form a stable lubricant film owing to the matching insurface energies between the solid and lubricant (i.e. ΔE₁>0 and ΔE₂>0),where the rest of the regions remain unstable (i.e. ΔE₁<0 and/or ΔE₂<0).When a suitable immiscible liquid encounters the unstable lubricatingregion, it can displace the lubricant and remain trapped within thepatterned region.

Potential applications of patterned SLIPS include spatially definedpatterning of cells for tissue engineering, mechano-biology, and singlecell study, patterning of biological fluids, as well as high sensitivitybiological sensors. Other applications include microfluidics, controlledplacement of molecules or material without cross-contamination, etc.

Heterogeneous topologies or spatially-defined patterns of selectivewettability can be formed on a liquid-coated or liquid-infiltrated solidsubstrate (SLIPS). The regions or holes that allow selective wetting(e.g., of an aqueous phase) can allow, by way of non-limiting example,local culture of cells, bacteria patterning for single cell study.DNA/RNA patterning for genomic sequencing and identification, proteinpatterning, fluid condensation and collection, ice nucleation, ortransport of liquid through a SLIPS layer for sensing or drainagefunctions. The combination of these ultra-low adhesion and selectivewetting (or wicking) properties can be used for applications forpatterning of biological and non-biological substances, printing ofcharacters, creating liquid adhesives, or permeable/non-permeable solidsupport, or for the design of bandage or ‘breathing skin layer’biomedical materials.

General Scheme of Creating SLIPS

FIG. 2 illustrates a general scheme of creating SLIPS in accordance withcertain embodiments of the present disclosure. Some of these stepsillustrated in FIG. 2 can be combined and repeated; but in some casesthese steps can be skipped (e.g., porous Teflon does not require theconditioning step at all, just lubrication; if the solid is alreadyroughened, only functionalization might be required before lubrication;etc.). In one example, the scheme can be Original substrate→Surfaceconditioning steps→Lubrication to make SLIPS. In another example, thescheme can be Original surface→Surface roughening→Surfacefunctionalization→Lubrication. In yet another example, the scheme can beOriginal surface→Coating with a layer of a different material→Rougheningof the additive layer→Surface functionalization→Lubrication.

A list of exemplary surface conditioning methods is provided below:

1. Additive surface conditioning methods

-   -   bonding solid phase material (SLIPS or SLIPS-ready sheet, tape,        or laminate)    -   application of material using liquid phase coating (paint or        ink, spray, spin, dip, air brush, screen printing, inkjet        printing, electrospinning, rotary jet printing)    -   deposition or reaction of gas phase material (CVD, plasma,        corona, ALD, PVD, iCVD, oCVD)    -   sputtering or evaporation of metal or metal oxide, sulfides,        nitrides, mixed oxides, oxo/hydroxo compounds, silica    -   evaporation or gas phase deposition of organic small molecules        (parylene), polymers and other carbon-based materials (CNT,        graphite, amorphous carbon, soot, graphene,        buckminsterfullerene, diamond)    -   composite phase material deposition (particle or sacrificial        particle+binder)    -   electrodeposition or other solution phase growth of material        (conducting polymer, electroplated metal, electroless        deposition, electrophoretic deposition of particles,        surface-initiated polymerization, electrostatic assemblies,        surface chemistry reactions, mineralization)    -   gas phase growth of material (nanoparticles, nanofibers,        nanowires, nanotubes, microparticles, microfibers, microwires,        microtubes)    -   multiple layer deposition (repeated coating, layer-by-layer        deposition)    -   self-assembly of precursor material (minerals, small molecules,        biomolecules, polymers, nano/microparticles, colloids)    -   growth of layers by oxidation    -   fouling-based deposition (using fouling as the nanostructure        itself, e.g. bacterial biofilm, scaling, marine fouling)    -   transfer coating and printing (contact printing, pattern        transfer, LB film)    -   a polymer foam deposition onto the substrate, with or without an        optional promoter/adhesive layer by spraying of a        polymer/prepolymer mixture/solution/emulsion/suspension/reagent        or comonomer mixture that forms a porous/contiguous porousiopen        cell-type structured porous surface. The polymer can be chosen        from a number of commercially available polymers and their        mixtures, non-exhaustive examples including polyurethane,        polystyrene, latex foams, etc.    -   accordingly, the appropriately chosen lubricating liquids can be        spray-coated onto these polymer foams with or without additional        conditioning of the polymer surface.

2. Subtractive surface conditioning methods

-   -   mechanical/physical etching (sanding, sand and bead blasting,        machining, sputtering)    -   chemical etching (acid, base, solvent, gas, anodization,        parkerizing, black oxide formation)    -   chemical mechanical etching

3. Surface conditioning by shape change (deformation)

-   -   wrinkle, crack, crease, ridge, fold formation by mechanically or        acoustically induced change    -   swelling by solvent or lubricant or a solution containing        chemical additives (oligomers, polymers, gels, etc.)    -   imprinting

4. Chemical surface conditioning methods

-   -   formation of covalent bonding    -   formation of ionic bonding    -   formation of complex/dative bonding    -   formation of self-assembled monolayers through the formation of        sulfide bonds, oxide bonds, silane, phosphate, phosphonate,        carboxylate, sulfonate, amine, etc.)    -   formation of non-specific adsorption and van-der-Waals        interactions    -   change of chemical affinity by physisorbed material-change of        chemical affinity by oxidation or reduction, electrochemical        reactions    -   growth (grafting from) of material    -   attachment (graft to) of material    -   growth and attachment (grafting through) of material    -   homogeneous chemicals    -   bi- or multi-functional chemical modifiers (zwitter ionic, block        co-polymer, switchable molecules) and their solutions    -   chemical structural transformation, recrystallization (e.g.        Boehmitization)

5. Physical surface conditioning methods

-   -   thermal (heating or cooling in air, inert gas, water, steam,        solvents, vapors, supercritical fluids, annealing, sintering,        melting, crystallization, phase transformation, carbonization)    -   mechanical (compression, tension, shear, expansion, aeration,        foaming)    -   optical and energetic particles (laser ablation, gamma        irradiation, electron beam, charged particles beams, UV,        particle bombardment)    -   electrical (joule heating, electrochemistry)    -   acoustic (surface acoustic wave localization)

6. Biological surface conditioning methods

-   -   growth or alteration of surfaces using biomolecules

Kinetically Stable SLIPS

As described above, SLIPS are a class of materials which typically meetthe following three requirements:

-   -   1) the lubricating liquid (Liquid B) must imbibe into, wet, and        stably adhere within the substrate (Solid);    -   2) the solid must be preferentially wetted by the lubricating        liquid rather than by the liquid one wants to repel (Liquid A);        and    -   3) the lubricating and impinging test liquids must be        immiscible.

SLIPS meeting the above three requirements are generally consideredthermodynamically stable, meaning its SLIPS state does not tend tochange considerably over time.

These factors can be designed to be permanent or lasting for timeperiods sufficient for a desired life or service time of the SLIPSsurface or for the time till a reapplication of the partially depletedinfusing liquid is performed. In some situations, kinetically stableSLIPS, which are stable for a limited period of time and/or for limitednumber of exposures to the liquid(s) being repelled, can still offerperformance substantially better than that of conventional materials.The kinetic stability can be due to various factors (e.g., highviscosity, slow mixing of liquids having limited but still appreciablemutual solubility, timescale of dewetting of lubricant slower thantimescale of wetting and replacement of lubricant by liquid A etc.),while some relations described in the rigorous thermodynamics-basedequations (i.e., equations 1 and 2) are not satisfied. FIGS. 3A and 3Billustrate the comparison between a thermodynamically stable SLIPS witha kinetically stable (i.e., meta-stable) SLIPS in accordance withcertain embodiments of the present disclosure. There can be manyliquid/liquid/(functionalized) solid combinations that fall into thiscategory of kinetically stable (a.k.a., meta-stable) SLIPS. Many ofthese meta-stable SLIPS can offer cost-effective solutions withperformance exceeding that of known in the art materials. The imbibingliquid/solid surface functionalization methods can be chosen from arange offering not thermodynamically best, but kinetically adequatecombinations that are at the same time compatible with otherrequirements of the application in question, e.g. biocompatible,biodegradable, food-compatible and the like.

To maintain high immiscibility between Liquid A and Liquid B, thesolubility in either phase should preferably be <500 parts per millionby weight (ppmw). For example, the solubility of water (Liquid A) inperfluorinated fluid (Liquid B, e.g., 3M Fluorinert™) is on the order of10 ppmw; the solubility of water (Liquid A) in polydimethylsiloxane(Liquid B, MW=1200) is on the order of 1 ppm. SLIPS performance could bemaintained transiently with sparingly immiscible Liquid A and Liquid B.In this case, the solubility of the liquids in either phase is <500parts per thousand by weight (ppthw). For solubility of >500 ppthw, theliquids can be considered miscible. The following Table 1 containsexamples of kinetically stable combinations of SLIPS. “Y” indicates thatLiquid B forms a stable lubricating film, and does not get displaced byLiquid A; whereas “N” indicates that Liquid B is displaced by Liquid Aover time. The equilibrium angles, θ_(A) and θ_(B), are estimated fromthe respective averages of the measured advancing and receding angles onflat substrates from at least three individual measurements. R, γ_(A),γ_(B) represent the roughness factor of the substrate and the surfacetensions of Liquid A and B, respectively.

TABLE 1 Stable Film? Solid Liquid A Liquid B R γ_(A) γ_(B) θ_(A) θ_(B) ΔE₀ Theory Exp Epoxy H₂O FC-70 2 72.6 17.1 83.7 28.1 7.1 Y Y Epoxy H₂OFC-70 1 72.6 17.1 83.7 28.1 7.1 Y N Silicon C₁₆H₃₄ H₂O 1 27.2 72.6 9.87.2 45.2 Y N Silicon C₁₀H₂₂ H₂O 1 23.6 72.6 4.2 7.2 48.5 Y N SiliconC₈H₁₈ H₂O 1 21.4 72.6 0 7.2 50.6 Y N Silicon C₆H₁₄ H₂O 1 18.6 72.6 0 7.253.4 Y N Silicon C₅H₁₂ H₂O 1 17.2 72.6 0 7.2 54.9 Y N

A meta-stable state is created when the lubricant's low surface tensionwets the surface but a “lock in”, that is, the energetical minimumsituation is not supported by the surface chemistry. As a result, theSLIPS state will eventually break down upon addition of a second liquid.However, this may take time, so a meta-stable slips surface can becreated even though the conditions for thermodynamic stability are notsatisfied. A meta-stable state could also be created by damaging thesurface to an extend that the supporting roughness is not high enough toallow for a lock in. FIG. 3C further illustrates an exemplarymeta-stable SLIPS state that is created by patterning the structuredsolid in a way that thermodynamically stable SLIPS surfaces arecoexisting with surface regions that do not favor lubricant lock in. Theupper part shows a scheme; the lower parts show photographs offluorinated surfaces (support SLIPS) patterned with hydrophilic patches(do not support SLIPS) consisting of 100 μm dot arrays (left), 500 μmdot arrays (middle) and 1 mm dot arrays (right). The latter two clearlyshow pinning (i.e. the thermodynamically stable situation as shown inthe scheme is reached in the course of the time the droplet needs topass the surface) while the first one shows SLIPS conditions in ameta-stable case (i.e. the hydrophilic parts are not wetted by octane inthe timescale of the droplet sliding down even though it would bethermodynamically favorable).

Object A

As noted previously, a wide range of materials can be repelled by theslippery surfaces of the present disclosure. For example, Object A caninclude polar and non-polar Liquids A, their mixture, and theirsolidified forms, such as hydrocarbons and their mixtures (e.g., frompentane up to hexadecane and mineral oil, aromatic liquids such asbenzene, toluene, xylene, ethylbenezene, aromatic liquids such asbenzene, toluene, xylene, ethylbenezene, paraffinic extra light crudeoil; paraffinic light crude oil; paraffinic light-medium crude oil;paraffinic-naphthenic medium crude oil; naphthenic medium-heavy crudeoil; aromatic-intermediate medium-heavy crude oil; aromatic-naphthenicheavy crude oil, aromatic-asphaltic crude oil, etc. and their oligomersand polymers), ketones (e.g., acetone, etc.), alcohols (e.g., methanol,ethanol, isopropanol, higher alcohols, propylene glycol, dipropyleneglycol, ethylene glycol, and glycerol, etc.), water (with a broad rangeof salinity, e.g., containing sodium chloride or bromide from 0 to 6.1M; potassium chloride or bromide from 0 to 4.6 M, water with highaffinity to scaling, such as having high concentration of Mg and Caions, etc), acids (e.g., concentrated hydrofluoric acid, hydrochloricacid, nitric acid, etc) and bases (e.g., potassium hydroxide, sodiumhydroxide, etc), ionic liquids, supercritical fluids, solutions of pureor mixed solutes, complex mixture of fluids and solids such as wine, soysauce and the like, ketchup and the like, olive oils and the like, honeyand the like, candle soot and paraffin, grease, soap water, surfactantsolutions, and frost or ice, etc. Object A can include biologicalobjects, such as insects, blood, small animals, protozoa, bacteria (orbacterial biofilm), viruses, fungi, bodily fluids and fecal matter,tissues, biological molecules (such as proteins, sugars, lipids, etc.),and the like. Object A can include gasses, such as natural gas, air orwater vapors. Object A can include solid particles (e.g., dust, smog,dirt, etc.) suspended in liquid (e.g., rain, water, dew, etc.) or gas.Object A can include non-biological objects, such as dust, colloidalsuspensions, spray paints, fingerprints, food items, common householditems, and the like. Object A can include adhesives and adhesive films.The list is intended to be exemplary and the slippery surfaces of thepresent disclosure are envisioned to successfully repel numerous othertypes of materials and materials combinations.

In certain embodiments, more than one different Object A can berepelled. In certain embodiments, the combination of two or more ObjectsA may together be more readily repelled as compared to just one ObjectA.

Liquid B

Liquid B (alternatively referred to as the “lubricant” through thespecification) can be selected from a number of different materials, andis chemically inert with respect to the Object A. Liquid B flows readilyinto the surface recesses of the roughened surface and generallypossesses the ability to form an ultra-smooth surface overcoat whenprovided over the roughened surface. In certain embodiments, Liquid Bpossesses the ability to form a substantially molecularly flat surfacewhen provided over a roughened surface. The liquid can be either a pureliquid, a mixture of liquids (solution), or a complex fluid (i.e., aliquid+solid components such as lipid solutions). For instance, FIG. 6shows a replication process to reproduce the morphology of the SLIPSsurface. First, a porous solid was infiltrated with Liquid B (e.g.,perfluorinated fluid). Then polydimethylsiloxane (PDMS) was cured overthe Liquid B layer to obtain a negative replica of the SLIPS surface.Then, epoxy resin (e.g., UVO 114, Epotek) was used to obtain a positivereplica using the PDMS negative replica. Then metrology analysis wascarried out with an atomic force microscope. As shown, the averageroughness of the positive replica surface was less than 1 nm, where theroughness represents an upper bound for the actual roughness of Liquid Bas this reaches the physical roughness limits for flat PDMS and UVO 114epoxy resin. Nonetheless, it is evident from the roughness analysis thatLiquid B overcoats the surface topographies of the porous solid, forminga nearly molecularly smooth surface.

In certain other embodiments, Liquid B possesses the ability to form asubstantially molecularly or even atomically flat surface when providedover a roughened surface.

In other embodiments, the lubricant layer follows the topography of thestructured surface and forms a conformal smooth coating (e.g., insteadof forming a smooth layer that overcoats all the textures). For example,the lubricant may follow the topography of the structured surface if thethickness of the lubricant layer is less than the height of thetextures. In certain embodiments, conformal smooth lubricant coating,which follows the topography of the structured surface and can showsignificantly better performance than the underlying substrate that wasnot infused with the lubricant.

Liquid B can be selected from a number of different liquids. Forexample, perfluorinated or partially fluorinated hydrocarbons ororganosilicone compound (e.g., silicone elastomer) or long chainhydrocarbons and their derivatives (e.g., mineral oil, vegetable oils)and the like can be utilized. In particular, the tertiaryperfluoroalkylamnines (such as perfluorotri-n-pentylamine. FC-70 by 3M,perfluorotri-n-butylamine FC-40, etc), perfluoroalkylsulfides andperfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers(such as FC-77) and perfluoropolyethers (such as Krytox family oflubricants by DuPont, Fomblin family of lubricants by Solvay),perfluoroalkylphosphines and perfluoroalkylphosphineoxides as well astheir mixtures can be used for these applications, as well as theirmixtures with perfluorocarbons and any and all members of the classesmentioned. In addition, long-chain perfluorinated carboxylic acids(e.g., perfluorooctadecanoic acid and other homologues), fluorinatedphosphonic and sulfonic acids, fluorinated silanes, and combinationsthereof can be used as Liquid B. The perfluoroalkyl group in thesecompounds could be linear or branched and some or all linear andbranched groups can be only partially fluorinated. In addition,organosilicone compounds such as linear or branched polydimethylsiloxane(PDMS) (e.g. Momentive Element family silicone lubricants, Siltechsilicone lubricants), polydiethylsiloxane (PDES),methyltris(trimethoxysiloxy) silane, phenyl-T-branchedpolysilsexyquioxane, and copolymers of side-group functionalizedpolysiloxanes (e.g. Pecosil silicone lubricants) and combinationsthereof can be used as Liquid B. In addition, various low molecularweight (up to C14) hydrocarbons (e.g. smokeless paraffin, Isopar™),long-chain (C15 or higher) alkyl petroleum oils or “white oils” (e.g.paraffin oils, linear or branched paraffins, cyclic paraffins, aromatichydrocarbons to petroleum jelly and wax), and raw or modified vegetableoils and glycerides and combinations thereof can be used as Liquid B.

In certain embodiments, Liquid B has a high density. For example, LiquidB has a density that is more than 0.5 g/cm³, 1.0 g/cm³, 1.6 g/cm³, oreven 1.9 g/cm³. In certain embodiments, the density of Liquid B isgreater than that of Object A to enhance liquid repellency. High densityfluids reduce the tendency of any impacting liquid to ‘sink’ below thesurface of Liquid B and to become entrained therein. For Object A thatis smaller than its capillary length (assume Object A is in liquidform), it is possible that the Liquid B has a density lower than that ofthe Object A, where the SLIPS formed by Liquid B can remain functional.

In certain embodiments, Liquid B has a low freezing temperature, such asless than −5° C., −25° C., or even less than −80° C. Having a lowfreezing temperature will allow Liquid B to maintain its slipperybehavior at reduced temperatures and to repel a variety of liquids orsolidified fluids, such as ice and the like, for applications such asanti-icing surfaces.

In certain embodiments, Liquid B can have a low evaporation rate, suchas less than 1 nm/s, less than 0.1 nm/s, or even less than 0.01 nm/s ofthe thickness of the lubricant per a given area. Taking a typicalthickness of Liquid B to be about 10 μm and an evaporation rate of about0.01 nm/s, the surface can remain highly liquid-repellant for a longperiod of time without any refilling mechanisms.

FIGS. 7A to 7C demonstrates the self-healing features of SLIPS. Incertain embodiments, the lifetime of the surface can be further extendedby using a self-refilling mechanism as illustrated in FIG. 7D.

Experimentally, it is observed that Liquid A can become highly mobile onthe surface of Liquid B when the kinematic viscosity of Liquid B is lessthan 1 cm²/s. Since liquid viscosity is a function of temperature (i.e.,liquid viscosity reduces with increasing temperature), choosing theappropriate lubricant that operates at the aforementioned viscosity(i.e. <1 cm²/s) at specific temperature range is desirable.Particularly, various different commercially available Liquid B can befound at the specified viscosity, such as perfluorinated oils (e.g., 3M™Fluorinert™ and DuPont™ Krytox® oils), at temperatures ranging from lessthan −80° C. to greater than 260° C. For example, the temperaturedependence of liquid viscosity of DuPont Krytox oils is shown in Table 2as a specific example (note: data is provided by the manufacturer ofDuPont Krytox oils).

TABLE 2 Temperature dependence of liquid viscosity of DuPont KrytoxOils. Viscosity (cm²/s) Temperature Krytox Krytox Krytox Krytox KrytoxKrytox Krytox Krytox (° C.) 100 101 102 103 104 105 106 107 20 0.1240.174 0.38 0.82 1.77 5.22 8.22 15.35 40 0.055 0.078 0.15 0.30 0.60 1.602.43 4.50 100 — 0.02  0.03 0.05  0.084 0.18 0.25 0.42 204 — — — — — 0.031 0.041 0.06 260 — — — — — — 0.024 0.033

Liquid B can be deposited to any desired thickness. A thickness ofLiquid B which is on the order of the surface roughness peak-to-valleydistance of the porous substrate provides good liquid-solid interactionbetween the substrate and Liquid B. When the solid substrate is tiltedat a position normal to the horizontal plane, liquid layer withthickness below a characteristic length scale can maintain goodadherence to the roughened surface, whereas liquid layers above thecharacteristic length can flow, creating flow lines (surface defects)and disrupting the flatness of the fluid surface. For example,non-limiting thicknesses for the fluid layer (as measured from thevalleys of the roughened surface are on the order of 5-20 μm when thepeak to valley height is ˜5 μm.

In certain embodiments, Object A (i.e., the test liquid) and Liquid B(i.e., the functional liquid layer) may be immiscible. For example, theenthalpy of mixing between Object A and Liquid B may be sufficientlyhigh (e.g., water and oil) that they phase separate from each other whenmixed together.

In certain embodiments, Liquid B can be selected such that Object A hasa small or substantially no contact angle hysteresis. Liquid B of lowviscosity (i.e., <1 cm²/s) tends to produce surfaces with low contactangle hysteresis. For example, contact angle hysteresis less than about5°, 2.5°, 2°, or even less than 1° can be obtained. Low contact anglehysteresis encourages test Object A sliding at low tilt angles (e.g.,<5°), further enhancing liquid repellant properties of the surface. Themechanics of SLIPS surfaces are discussed in International PatentApplication Nos. PCT/US2012/21928 and PCT/US2012/21929, both filed Jan.19, 2012, the contents of which are hereby incorporated by reference intheir entireties.

Roughened Surface

As used herein, the term “roughened surface” includes both the surfaceof a three-dimensionally porous material (such as a fibrous net) as wellas a solid surface having certain topographies, whether they haveregular, quasi-regular, or random patterns, or largely smooth surfaceswith very small surface features.

In certain embodiments, the roughened surface may have a roughnessfactor, R, greater than or equal to 1, where the roughness factor isdefined as the ratio between the real surface area and the projectedsurface area. For complete wetting of Liquid B to occur, it is desirableto have the roughness factor of the roughened surface to be greater orequal to that defined by the Wenzel relationship (i.e. R≧1/cos θ where θis the contact angle of Liquid B on a flat solid surface). For example,if Liquid B has a contact angle of 50° on a flat surface of a specificmaterial, it is desirable for the corresponding roughened surface tohave a roughness factor greater than ˜1.5. It is noteworthy that the“slipperiness” of the surface generally increases with the increase of Rfor the same material.

In certain embodiments, the presence of a roughened surface can promotewetting and spreading of Liquid B over the roughened surface, as isdemonstrated in FIG. 4. FIG. 4(A) shows a droplet 300 of Liquid B(FC-70, a high boiling point, water-insoluble perfluorinatedtrialkylamine) on a flat, unstructured surface 310 prepared from asilanized epoxy resin. The dashed line represents the location of theupper surface of the substrate. While the droplet spreads on thesurface, it retains its droplet shape and has a finite contact angle.FIG. 4(B) shows the same Liquid B on an exemplary roughened surface 320of the same composition (silanized epoxy resin). The presence of theroughened surface promotes the spreading out and filling in of thedroplet into the valleys of the roughened surface. As shown, thenanostructures greatly enhance the wetting of the Liquid B on thesurface, creating a uniformly-coated slippery functional layer over thetopographies.

In certain embodiments, the roughened surface can be manufactured fromany suitable materials. For example, the roughened surface can bemanufactured from polymers (e.g., epoxy, polycarbonate, polyester,nylon, Teflon, polysulfone, polydimethylsiloxane, etc.), metals (e.g.,aluminum, steel, stainless steel, copper, bronze, brass, titanium, metalalloys, iron, tungsten), plastics (e.g., high density polyethylene(HDPE); low density polyethylene (LDPE); polypropylene (PP); polystyrene(PS); polyethylene terephthalate (PET))), sapphire, glass, carbon indifferent forms (such as diamond, graphite, carbon black, etc.),ceramics (e.g., alumina, silica, titania, zirconia, etc), and the like.For example, fluoropolymers such as polytetrafluoroethylene (PTFE),polyvinylfluoride, polyvinylidene fluoride, Viton, fluorinated ethylenepropylene, perfluoropolyether, and the like can be utilized. Inaddition, roughened surface can be made from materials that havefunctional properties such as conductive/non-conductive, andmagnetic/non-magnetic, elastic/non-elastic,light-sensitive/non-light-sensitive materials. A broad range offunctional materials can make SLIPS.

In certain embodiments, the roughened surface may be the porous surfacelayer of a substrate with arbitrary shapes and thickness. The poroussurface can be any suitable porous network having a sufficient thicknessto stabilize Liquid B, for example a thickness 50+ nm, or the effectiverange of intermolecular force felt by the liquid from the solidmaterial. The substrates can be considerably thicker, however, such asmetal sheets and pipes. The porous surface can have any suitable poresizes to stabilize the Liquid B, such as from about 10 nm to about 2 mm.Such a roughened surface can also be generated by creating surfacepatterns on a solid support of indefinite thickness.

Many porous materials are commercially available, or can be made by anumber of well-established manufacturing techniques. For example, PTFEfilter materials having a randomly arranged three-dimensionallyinterconnected network of holes and PTFE fibrils are commerciallyavailable. FIGS. 5A to 5E illustrate some non-limiting exemplaryembodiments of suitable porous materials.

The roughened surface material can be selected to be chemically inert toLiquid B and to have good wetting properties with respect to Liquid B.In certain embodiments, Liquid B (and similarly Object A) may benon-reactive with the roughened surface. For example, the roughenedsurface and Liquid B (or Object A) can be chosen so that the roughenedsurface does not dissolve upon contact with Liquid B (or Object A). Inparticular, perfluorinated liquids (Liquid B) work exceptionally well torepel a broad range of Liquids A and their solidified forms, such aspolar and non-polar Liquids A, their mixtures, and their solidifiedforms, such as hydrocarbons and their mixtures (e.g., from pentane up tohexadecane and mineral oil, aromatic liquids such as benzene, toluene,xylene, ethylbenezene, paraffinic extra light crude oil; paraffiniclight crude oil; paraffinic light-medium crude oil;paraffinic-naphthenic medium crude oil; naphthenic medium-heavy crudeoil; aromatic-intermediate medium-heavy crude oil; aromatic-naphthenicheavy crude oil, aromatic-asphaltic crude oil, etc. and their oligomersand polymers), ketones (e.g., acetone, etc.), alcohols (e.g., methanol,ethanol, isopropanol, higher alcohols, propylene glycol, dipropyleneglycol, ethylene glycol, and glycerol, etc.), water (with a broad rangeof salinity, e.g., sodium chloride from 0 to 6.1 M; potassium chloridefrom 0 to 4.6 M, etc.), acids (e.g., concentrated hydrofluoric acid,hydrochloric acid, nitric acid, etc) and bases (e.g., potassiumhydroxide, sodium hydroxide, etc), ionic liquids, supercritical fluids,solutions of pure or mixed solutes, complex mixture of fluids and solidssuch as wine, soy sauce and the like, ketchup and the like, olive oilsand the like, honey and the like, grease, soap water, surfactantsolutions, etc. Object A can include biological objects, such asinsects, blood, small animals, protozoa, bacteria (or bacterialbiofilm), viruses, fungi, bodily fluids and tissues, lipids, proteinsand the like. Object A can include solid particles (e.g., dust, smog,dirt, etc.) suspended in liquid (e.g., rain, water, dew, etc.). Object Acan include non-biological objects, such as dust, colloidal suspensions,spray paints, fingerprints, food items, common household items, frost,ice and the like. Object A can include adhesives and adhesive films. Thelist is intended to be exemplary and the slippery surfaces of thepresent disclosure are envisioned to successfully repel numerous othertypes of materials.

In addition, the roughened surface topographies can be varied over arange of geometries and size scale to provide the desired interaction,e.g., wettability, with Liquid B. In certain embodiments, themicro/nanoscale topographies underneath the Liquid B can enhance theliquid-wicking property and the adherence of Liquid B to the roughenedsurface. As a result, the Liquid B can uniformly coat the roughenedsurface and get entrapped inside at any tilting angles.

In addition to the desired topography, the roughened surface can beconditioned, modified or functionalized to acquire necessary properties(e.g., affinity, wettability) towards lubricating Liquid B. For example,the surface can be modified to expose hydrophilic/polar/charged chemicalgroups, including but not limited to hydroxyl, amine, carboxyl, sulfate,sulfonate, phosphate, phosphonate, carboxylate, ammonium, making itcompatible with wetting by polar liquids, such as water and aqueoussolutions of different pH and ionic strength, ionic liquids and theirmixtures. Imbibing the thus modified roughened surface with polarliquids will result in oleophobic SLIPS. In another example, the surfacecan be modified to expose hydrophobic/non-polar/non-charged chemicalgroups or chains, including but not limited to alkyl, cycloalkyl, aryl,aralkyl, alkene, substituted silyl, that can be linear, branched orcyclic, making it compatible with wetting by non-polar liquids, such ashydrocarbons, natural, mineral or silicone oils, petroleum fractions,molecules containing aromatic, cycloaliphatic, paraffinic chains ofvarious molecular weight, length and branching and their mixtures.Imbibing the thus modified roughened surface with non-polar liquids willresult in hydrophobic SLIPS. In yet another example, the surface can bemodified to expose fluorinated chemical groups or chains, including butnot limited to partially or fully fluorinated hydrocarbon chains,perfluoropolyethers and other fully or partially fluorinated liquidsdescribed in more detail in the description below. Imbibing the thusmodified roughened surface with fluorinated liquids will result inomniphobic (both hydrophobic and oleophobic) SLIPS. General types andprinciples of surface conditioning, modification, and functionalizationare classified in the description in this document. Depending on thematerial of the roughened surface, the applicable conditioning andfunctionalization methods can include physical, chemical treatment aswell as a combination of any number of physical and chemical stepsdetailed in the following sections. In addition, a combination of notperfectly matched surface functionalization and lubricant can also beused. For example, a robust ice-repellent SLIPS can be made byapplication of silicone lubricant on fluorinated surface.

Applications

Numerous different applications for SLIPS can be envisioned wheresurface that repels a wide range of materials is desired. Somenon-limiting exemplary applications are described below.

Example 1 Protective Fabric Materials

A slippery surface can be applied in functional protectivefabrics/gloves/blankets/towels/laboratory-clothing, roofs, domes andwindows—in architecture, tent, swim-suits, wet suits, rain-coats,tactical gear, military clothing, firefighter clothing, and the like.These functional fabric materials can serve as physical barriers andused to repel a broad range of hazardous fluids/solids, such as acid,base, oxidizing/reducing agents, toxic substances, highly flammableliquids, high temperature fluids, burning oils, fire/flame, lowtemperature fluids, ice, and frost.

SLIPS can be applied onto common fabric materials, such as naturalcotton, and synthetic fabrics (e.g., polytetrafluoroethylene (PTFE),polyethylene terephthalate (PET), polypropylene, polyester, acrylic,nylon, latex, rayon, acetate, olefin, spandex, kevlar). In thisexemplary application, the lubricating fluids can be chosen from a broadrange of perfluorinated fluids (including but not limiting to thetertiary perfluoroalkylamines (such as perfluorotri-npentylamine, FC-70by 3M, perfluorotri-n-butylamine FC-40, etc), perfluoroalkylsulfides andperfluoroalkylsulfoxides, perfluoroalkylethers, perfluorocycloethers(like FC-77) and perfluoropolyethers (such as KRYTOX family oflubricants by DuPont), perfluoroalkylphosphines andperfluoroalkylphosphineoxides as well as their mixtures can be used forthese applications); polydimethylsiloxane and their functionalmodifications; food compatible liquids (including but not limiting toolive oil, canola oil, coconut oil, corn oil, rice bran oil, cottonseedoil, grape seed oil, hemp oil, mustard oil, palm oil, peanut oil,pumpkin seed oil, safflower oil, sesame oil, soybean oil, sunflower oil,tea seed oil, walnut oil, and a mixtures of any of the above oils).

Depending on the chemical affinity of the solid to the lubricants withrespect to the fluids one want to repel, chemical functionalization androughening of the solid can further enhance the chemical affinity. Mostof the natural cottons and synthetic fibers are woven into highlytextured, porous surfaces (e.g., see FIG. 8), in which the solid supportcan provide enough surface area for the adherence of the lubricatingfluids. When these materials are converted into SLIPS, appropriatechemical functionalization schemes can enhance the chemical affinitywith the lubricants. The following are a few examples of the chemicalfunctionalization schemes for materials where further chemicaltreatments can be applied.

1) Fluorosilanization of PET: To fluorosilanize PET to create a highlyfluorinated surface, one could start with amines (e.g.,3-aminopropyltrialkoxysilanes) which can react readily with PET toactivate the ester linkages on the surface. Amine functionalized PET canreact with tetraethylorthosilicate (TEOS) to create surface hydroxylgroups which can condense with silanes (e.g.,tridecafluoro-1,1,2,2-tetrahydrooctyl)-trichlorosilane). Protocols toachieve the aforementioned steps can be referred to A. Y. Fadeev and T.J. McCathy, Langmuir 14, 5586-5593 (1998).

2) Deposition of chemically functionalized silica onto fabric (bothnatural and synthetic): Another approach to chemically functionalizefabrics directly is through in-situ synthesis of silica particles withamine groups at the surface of the fibers through Stober method (Stober,W.; Fink, A.; Bonn, E. J. Colloid Interface Sci. 1968, 26, 62). Throughthis method, the silica microparticles could covalently bond to thesurface of natural and synthetic fabrics (See FIGS. 9A-9C). With thecreation of the silica surface, one could further fluorosilanize thesurface through the vapor/liquid phase silanization methods.

With chemically functionalized fabrics, one can apply the lubricatingfluids by a broad range of deposition methods, such as dip/spraycoatings. With these slippery coatings, it was shown that they caneffectively repel a broad range of aqueous, hydrocarbons, and complexfluids. For example, FIGS. 10A-10C demonstrate SLIPS fabrics forfunctional clothing against various complex fluids and high temperaturefluids in accordance with certain embodiments.

Example 2 Self-Cleaning and Self-Replenishing SLIPS Optical Coating

Optical parts suffer from contamination by dust particle, grease, andother complex liquids. SLIPS coating can be applied to keep optics freefrom fouling. With combined mechanism of removing condensed water onSLIPS coating layer, tilt, air flow, or vibration, condensed water canalso be removed effortlessly.

FIG. 11 demonstrates photographs of a fog test on a 60° C. water. Theleft half of the glass is uncoated; the right half of the glass is SLIPScoated. The left photo shows the result after 10 seconds of fog test.The right photo shows the result after 3 minutes. FIG. 12 shows aschematic illustration of a fog-free optical viewing cover formicroscope.

An optical quality SLIPS coating can prevent fouling by foreign materialand condensation while the lubricating liquid can be replenished fromsurrounding materials such as the O-rings, bearings, and housing holdingthe optics in place. For example, a silicone lubricant can beinfiltrated in an O-ring made of silicone rubber from which thelubricant can be continuously supplied to replenish and coated surfaceautomatically or manually by external control (e.g., by turning a screwto squeeze the lubricant from the reservoir). FIG. 13 contains aschematic illustration of a circular optics encased in alubricant-containing O-ring serving as a reservoir in accordance withcertain embodiments.

FIG. 14 demonstrates a photograph of camera lens protectors withoutcoating (left) and with coating (right), in accordance with certainembodiments. When water is applied on the lens protector, the waterspreads on the coated lens protector but beads up on the coated lensprotector. When the coated lens protector is tilted, the water dropletslides and cleans dusts off the surface. FIG. 15 further demonstrates aphotograph of camera lens protectors without coating (left) and withcoating (right), in accordance with certain embodiments. After the lensprotector is tilted, the water droplet spreads and mostly remains on theuncoated lens protector; while the water droplet slids to the bottom ofthe coated lens protector. The coating can also provide ananti-reflective feature due to the nanostructure on the surface of thecoated lens.

Example 3 SLIPS Containers

A SLIPS layer can be coated onto the inner and/or outer surface ofcontainers, such as bottles, bags, and tubes, that are made out ofcommon plastics (i.e., high density polyethylene (HDPE); low densitypolyethylene (LDPE); polypropylene (PP); polystyrene (PS); polyethyleneterephthalate (PET); polycarbonate (PC); polylactic aid (PLA); polyvinylchloride (PVC)) plastic-lined metal containers, metal containers, glasscontainers, ceramic containers, or containers of composite materials.Lubricants can be chosen from food and cosmetics compatible liquids,including but not limiting to olive oil, canola oil, coconut oil, cornoil, rice bran oil, cottonseed oil, grape seed oil, hemp oil, mustardoil, palm oil, peanut oil, pumpkin seed oil, safflower oil, sesame oil,soybean oil, sunflower oil, tea seed oil, walnut oil, and a mixtures ofany of the above oils. In another embodiment, the lubricants can bechosen from biocompatible liquids, including but not limited to fattyacids, glycerolipids, glycerophospholipids, sphingolipids, sterollipids, prenol lipids, saccharolipids, polyketides, and their solutions.The lubricating oils can be applied to the interior of the bottles orbags by spray-coating, dip-coating, and vapor deposition process etc.

In certain embodiments, for the complex fluid and paste-like mixtures(ketchup, mayonnaise, paints, shampoos, conditioners, tooth paste, theinner surface of the container or part thereof will be designed to haveappropriate roughness and chemical functionalization so as to ensure itshigh affinity towards one or more major liquid components of the complexfluid/paste (like various food grade natural oils (olive, vegetable,sunflower, canola, etc. and their mixtures) for ketchup and mayonnaise;oil base (mixture of aliphatic and aromatic hydrocarbons and short chainketones) of oil paints; essential fatty acids, fatty alcohols, siliconepolymers and their mixtures for shampoos and conditioners) and therebyproduce the needed overlaying liquid layer inherently within thecontainer.

In certain embodiments a range of food and biocompatible, widely used infood/medical/healthcare applications oligomers, polymers, copolymers ofvarious molecular weights and chemical structures and their blends canbe used for making a roughened surface and for its functionalization bychemical and/or deposition means. The examples include, but are notlimited to polylactic acid, polyglycolic acid, polylactide-co-glycolide,poly-ethyleneglycol, polyethyleneoxide, polypropyleneoxide and theircopolymers, polysulfone, polytetrafluoroethylene, other fully andpartially fluorinated polymers, copolymers and oligomers, as well aspolyolefins, polyesters, polyacetals, polyvinylidenefluoride,polyacrylates, polyurethanes, silicones, polycarbonate. An additionalnon-exhaustive list of polymers used in food industry, their trade namesand approval status by various regulatory bodies is given in FIG. 16A(adapted from Food Processing—Handling Brochure 2011 by ProfessionalPlastics, Inc. which is incorporated here as a reference in itsentirety.

After the slippery coatings are applied on the plastic bottles, it isshown that the bottles can be capable of repelling a broad range ofcomplex food fluids and cosmetics, including but not limiting toketchup, mayonnaise, honey mustard dressing, Caesar dressing, ranchdressing, thousand island dressing, blue cheese dressing. Frenchdressing, ginger dressing, honey Dijon, Italian dressing, Louisdressing, vinaigrette, Russian dressing, and a mixture of the abovecomponents. The lubricating oils can be chosen from an oilcomponent/mixture of the oil components that are present in the foodfluids or cosmetics that one wants to repel (where the oil component isimmiscible with the other contents that are present in the food fluidsor cosmetics). The common oil component can allow for theself-replenishing and self-lubricating effects of the slippery coatingswithin the bottles. FIG. 16B illustrates SLIPS-treated bottles repellingcomplex food products, such as ketchup and mayonnaise. FIG. 16Csimilarly shows a SLIPS-treated plastic bag repelling warm oatmeal.

FIG. 16D shows a SLIPS-treated ice tray repelling ice.

In yet another example, after the slippery coatings are applied on theplastic bags, it is shown that the bags can be capable of repelling abroad range of 1) biological solids/fluids, including but not urine,blood, feces, whole blood, plasma, serum, sweat, feces, urine, saliva,tears, vaginal fluid, prostatic fluid, gingival fluid, amniotic fluid,intraocular fluid, cerebrospinal fluid, seminal fluid, sputum, ascitesfluid, pus, nasopharengal fluid, wound exudate fluid, aqueous humour,vitreous humour, bile, cerumen, endolymph, perilymph, gastric juice,mucus, peritoneal fluid, pleural fluid, sebum, vomit, and combinationsthereof; 2) complex food fluids including but not limited to ketchup,mayonnaise, honey mustard dressing, Caesar dressing, ranch dressing,thousand island dressing, blue cheese dressing, French dressing, gingerdressing, honey Dijon, Italian dressing, Louis dressing, vinaigrette,Russian dressing, oatmeals, and a mixture of the above components; 3)cosmetics including but not limited to body/facial lotions. Thelubricating oils can be chosen from an oil component/mixture of the oilcomponents that are present in the food fluids or cosmetics that onewants to repel (where the oil component is immiscible with the othercontents that are present in the food fluids or cosmetics). The commonoil component can allow for the self-replenishing and self-lubricatingeffects of the slippery coatings within the containers.

Example 4 Fragrance/Flavor-Enhanced SLIPS

Slippery surfaces with fragrance or flavor enhancement, which can beapplied onto polymeric, ceramic, metallic or composite surfaces fordifferent industrial and medical applications where imparting of apleasant odor, masking of an unpleasant odor, imparting or supporting ofa particular flavor or taste or any combination of the above effects arerequired. The key novelty of the invention is the incorporation oftailor-made lubricants that in addition to their ability to befunctional elements of the slippery, liquid/solid/complexfluid-repellant surfaces, possess the desired odor/taste/flavorcharacteristics.

In this embodiment, a slippery, repellant coating is that includes achemically or physically modified/conditioned/functionalized structuredsolid surface having a desired degree of roughness that is infused witha lubricating fluid is described. Various modifications of the conceptthat are based on hybrid materials that are pre-swollen with saidlubricating fluid are included and covered by this embodiment, as well.

The lubricating fluids can be chosen from a variety of natural andsynthetic oils, a subset of which would include food orbiologically-compatible liquids, including but not limited to olive oil,canola oil, coconut oil, corn oil, rice bran oil, cottonseed oil, grapeseed oil, hemp oil, mustard oil, palm oil, peanut oil, pumpkin seed oil,safflower oil, sesame oil, soybean oil, sunflower oil, tea seed oil,walnut oil, and a mixtures of any of the above oils.

Another subset of lubricating liquids includes synthetic oligomeric andpolymeric long-chain hydrocarbon-, silicone-, fully or partiallyfluorinated materials with carbon-carbon, carbon-nitrogen,carbon-oxygen, carbon-sulfur, carbon-phosphorus and othercarbon-heteroatom linkages and combinations thereof, with varyingmolecular weights, linear or having varying degrees of branching andvarying relative proportions of the different types of co-monomers orlinkages present within their structures. These lubricating oils can befurther modified by the addition of or functionalization with odor- orflavor-imparting components or modifiers to provide the desiredmulti-sensory functions, such as imparting of a pleasant odor, maskingof an unpleasant odor, imparting or supporting of a particular flavor ortaste or any combination of the above effects.

As shown in FIG. 17, these odor- or flavor-imparting components can beadded to the base oil, as such, to be dissolved (Method 1), emulsified,or otherwise dispersed (Method 3); alternatively, they can be includedtogether with specially-engineered carrier matrices that are formulatedfor slow release (Method 2); they can also be chemically attached to themolecules comprising the lubricating liquid. There is a wide variety ofthe fragrant and flavor materials to be chosen from natural,nature-identical and fully synthetic ones, including those produced bymeans of biotechnology.

Those skilled in art will recognize that the list of the chemicals usedin flavor, fragrance, cosmetics and food industries is extremely broad,so by the way of reference, two following exemplary sources are includedhere:

-   1. Rowe, D. J. (2005). Chemistry and Technology of Flavour and    Fragrance, John Wiley & Sons-   2. Berger, R. G. (2007). Flavours and Fragrances: Chemistry,    Bioprocessing and Sustainability, Springer.

A large proportion of fragrance chemicals are hydrophobic in nature andtherefore compatible/soluble with hydrophobic lubricating fluids. Commonclasses of hydrophobic fragrant chemicals include olefins, esters,ketones, long chain alcohols and aldehydes and many more. An exemplary,not meant to be limiting list of the typical molecules that could becombined with the non-polar lubricants includes, e.g., S-limonene,R-limonene, dipentene, phenethyl isobutyrate, phenethyl isovalerate,octanol, nonanol, or their mixtures etc. The fragrance/favor enhancedlubricating oils can be applied by spray-coating, dip-coating, and evenvapor deposition process etc. For certain embodiments, the fragrance orflavor enhancers are chosen such that they are biodegradable/withbiological origins, and with smells or flavors viewed positively andconsidered pleasant by a big proportion of the general population; theother important considerations are the cost and IP: there is a bignumber of industrially produced, inexpensive fragrant chemicals that areeither not patentable or are off patents, which can be used as art ofthe formulation of the fragrance-enhanced lubricants.

The fragrance/flavor-enhanced slippery surfaces described above arecapable of repelling a broad variety of aqueous-based complex fluidsincluding food and human excretes. The slippery surfaces can be coatedonto surfaces that are made out of common plastics (e.g., high densitypolyethylene (HDPE); low density polyethylene (LDPE); polypropylene(PP); polystyrene (PS); polyethylene terephthalate (PET); polyvinylchloride (PVC)), ceramics (e.g., glass), and metals (e.g., aluminum).

Such fragrance or flavor-enhanced SLIPS structures can be utilized asodor-neutralizer/fragrance enhancer for ostomy bags, sanitary andtoiletry products, toilet bowls, as well as fragrance/flavor enhancerfor food and cosmetic containers and other surfaces that come in contactwith materials that need to be repelled or move freely on the surfaceand where the resulting odor and/or flavor characteristics, when addedto the repellant behavior of the surfaces, add positively to the overallperformance and/or perception of the performance.

Example 5 SLIPS Gas Pipelines

According to Energy Information Administration, natural gas pipelinesconsume an average of two to three percent of throughput to overcomefrictional losses compared to electric transmission lines, which losesix to seven percent of the energy they carry due to electric resistance(Energy Information Administration, Frequently Asked Questions(national-level losses were 6.5 percent of total electricity dispositionin 2007), available athttp://tonto.eia.doe.gov/ask/electricity_faqs.asp#electric_rates2.)According to Interstate Natural Gas Association of America (InterstateGas Pipe Efficiency, Interstate Natural Gas Association of America,Washington, D.C, release date Nov. 1, 2010,http://www.ingaa.orgil1885/Reports/10927.aspx), one way to mitigatethese losses is to use internally coated pipes, that provide someimprovement at a cost of $2-$8 per foot depending on the pipe diameterand the coating used. In this example, internally coated pipe requiredless horsepower than uncoated pipe, reducing fuel from 1.627 to 1.452MMcf/d. For example, FIG. 18 illustrates pressure drop on internallycoated pipe as a function of flow in accordance with certainembodiments.

Drag and friction reducing SLIPS layers can be formed on a variety ofsubstrates for the applications involving gas flows. For example, aslippery coating of tubes and pipes can be formed based on SLIPS. Thegas is understood to include gas phase, liquefied, and supercriticalfluids that are subject to high flow rates and associated energy lossesdue to friction and drag. The examples of gases include but are notlimited to air, steam, liquefied natural gas (methane), liquefiedpetroleum gas, higher alkanes, ethylene, acetylene, higher alkenes andmixtures thereof, carbon monoxide, carbon dioxide, oxygen, hydrogen,inert gases (nitrogen, helium, and noble gases), reactive gases(halogens, hydrogen halides, ammonia, hydrazine, phosphine, arsine),pure and mixed halogenated hydrocarbons, pure and mixedhydrofluorocarbons, halogenated fluorocarbons, etc. In certainembodiments, mixtures of gases, both reactive and inert can be used(like synthesis gas—CO/H2) as well as the gaseous reactant mixtures,product mixtures and Side/waste streams.

A non-exhausting list of combinations of roughened material surfaces andmethods of their functionalization for retaining different lubricatingliquids are presented below. The surfaces are proposed to possess thedesired levels of roughness and when necessary further functionalized toensure that the lubricating liquid is immobilized and retained withinthe roughened surface. For all the examples below, one can, inprinciple, design onmiphobic slippery surfaces (those based onpolyfluorinated oils retained within roughened surfaces functionalizedto have a strong affinity to fluorinated molecules), hydrophobicslippery surfaces (those based on natural or synthetic/mineral oilsretained within roughened surfaces having hydrophobic (not necessarilyfluorine containing) functionalization), and oleophobic slipperysurfaces (those based on aqueous lubricating liquids retained within theroughened surfaces having appropriately functionalized hydrophilicsurface). The list below is not assumed to include only the mostrelevant materials for gas transporting pipes, but it rather includesseveral types of materials that may find application in thefriction/drag-reducing applications involving gas flows. It is alsoworth noting that the combinations included in this non-exhaustive listcan be applicable for all other applications, in addition to gas/fluiddrag and friction reduction.

1. Stainless steel, other steels can be modified by several methods:with silica or related oxide materials using atomic layer deposition orby sol-gel method, or electrochemically with a range of thiol-terminatedmolecules, or wet etching with acids catalyzed with iron thatselectively etches some portions with defined domain sizes present inthe alloy. The resulting anchor coatings can be used as such (as in thecase of thiol SAMs) or modified further using Si—OH (or related)functionalities of silica (or other ALD or sol-gel coating) or the headgroups of thiol SAMs. Fully, partly, or non-fluorinated functionalitiesintroduced this way can provide the stainless steel with the surfacechemistry suitable for retention of appropriately chosen lubricatingliquid. The lubricating liquid can then be selected, depending on thetarget application, from a variety of fluorinated oils ornon-fluorinated natural (olive oil, vegetable oils and such) orsynthetic liquids (higher hydrocarbons—aliphatic, aromatic, mixed,silicon oils and mixtures thereof).

2. Titanium, Tantalum, Niobium and other early and middle transitionmetal surfaces (generally covered with oxide layer) can befunctionalized with (polyfluoro)alkanephosphates/phosphonates/sulfonates/carboxylates that can form stableSAMs on their surface. The following modification with a lubricatingliquid and its choice are the same as above.

3. Aluminum surface modification can be done using a range of physical,chemical and electrochemical techniques. These can include controlledconductive polymer deposition and growth, ALD, sol-gel deposition,Boehmite formation, SAM formation similar to described above fortitanium and other metals, as well as silanization/fluorosilanizationfrom solution or gas phase. The following modification with alubricating liquid and its choice are the same as above.

4. Polymer surfaces, especially those that themselves are lackingpendant chemical functionalities, can use chemical (hydrolytic,high-temperature steam, strong acids, bases, oxidants) and/or plasmaetching to provide sufficient number of chemical functional group(hydroxyls, carboxyls) to allow one to install the desired surfacechemistry. However, in many cases, even the non-functionalized polymersurfaces are already compatible with a number of lubricating liquids. Inother cases, the combination of plasma treatment and ALD of silica orrelated materials can provide sufficient number of functionalizablereactive groups needed to modify the polymer surface enough to retainthe desired lubrication liquid. The functionalization can then becarried out using chlorosilane coupling, amide coupling, glicydylchemistry, etc.

5. Sapphire surface can use high-energy laser treatment to achieveinstallation of appreciable numbers of chemical functional groups.

6. Glass and related mixed oxide materials can be etched withappropriate etchant (e.g., HF, acid piranha) or plasma treated, ifnecessary, and then the Si—OH (or other related —OH) functionalities canbe used for further modifications using various chemical methods. Forexample, a range of commercially available fluorinated ornon-fluorinated chloro- or alkoxysilanes can be used to install thedesired surface chemistry. Fully, partly, or non-fluorinatedfunctionalities introduced this way will provide glass with the surfacechemistry suitable for retention of the appropriately chosen lubricatingliquid. The lubricating liquid can then be selected, depending on thetarget application, from a variety of fluorinated oils ornon-fluorinated natural or synthetic liquids and mixtures thereof.

Other potential applications of SLIPS can include inner surface of tubesand pipes used in gas transport systems, watch glasses within the gastransport systems, blades of wind turbines (the SLIPS-type coating maycombine the gas friction reduction and ice repelling), gas turbines, andgas lines in chemical and petroleum industries and civilian objects.

Example 6 Anti-Corrosive and Anti-Scaling Coatings

Many metal surfaces have issues with corrosion that create pitting,decarburization leading to cracks and mechanical breakdown of structurescaused by contact with acid, base, brine, oxidizing and reducingchemicals, and acid rain. In addition, metallic, plastic, ceramic, orcomposite pipelines and surfaces exposed to aqueous and non-aqueoussystems are subject to the growth of oxide, hydroxide or oxoacid scale(precipitation fouling) and the deposition of solid fouling commonlyfound in boilers and heat exchangers reducing thermal conduction and inreservoirs and wells in oil field deteriorating their productivity.Common industrial fouling deposits include calcium carbonate, calciumsulfate, calcium oxalate, barium sulfate, magnesium hydroxide, magnesiumoxide, silicates, aluminum oxide hydroxide, aluminosilicate, copper,phosphates, magnetite, or nickel ferrite. Solid deposits may also formon the surface of chemical reactors that decreases thermal conduction,induces undesirable chemical reactions such as oxidation,polymerization, carbonization, catalyzed by the metallic walls.

A SLIPS coating can prevent corrosion, scaling, and unwanted soliddeposition by creating repellent surfaces to various liquids and solids,in particular, liquids with high acidity or basicity, sea water,concentrated brine, and hard water. The coatings can be directly formedon some metals (e.g. aluminum) or by application of coating materials(e.g. sol-gel alumina based Boehmite) followed by appropriate chemicalfunctionalization and addition of immiscible lubricant. In certainembodiments, the lubricating fluid/appropriately functionalized surfacecombinations can be used as anti-corrosive protecting coatings for metaland metalized surfaces designed to resist the corrosion-inducingenvironments, both liquid (fresh, salt and sea water, highly corrosivechemical and waste streams) and otherwise (exposure to aggressivevapors, aerosols and mist through evaporation or convection).

FIG. 19 illustrates the time lapse of untreated Al (left) andSLIPS-coated Al (right) immersed in 1 M KOH solution at room temperatureshowing rapid degradation of untreated aluminum while coated Alessentially remains unchanged.

Example 7 SLIPS Surfaces for Fluid Collection

Efficient collection of water condensate can be important for a numberof industrial applications, such as heat transfer and dew collection.SLIPS surfaces have a very high mobility for even small water droplets,also cause a very rapid condensation of small water droplets from thevapor phase. Water droplets on conventional, hydrophobic surfaces have acontact angle >60°, and are not highly mobile. The edges of the dropletare pinned such that a reasonably high tilt angle of the substrate isrequired to move a droplet of some given size. Conversely, for avertically-oriented surface, a droplet must achieve a critical volumebefore becoming mobile (Vcrit). FIG. 20 (top) shows the steps involvedin the nucleation, coalescence and sliding of water droplets on aconventional hydrophobic surface. The Vcrit for SLIP surfaces is muchlower than for conventional hydrophobic surfaces (FIG. 20B, bottom).Therefore, water droplets coalesce and slide much more readily than on aconventional surface, and the efficiency and rate of condensationcollection is much higher. In addition, the condensed droplets on SLIPStend to suddenly run quickly due to the large energy gain fromcoalescence events which would have been used by friction on othersurfaces hence facilitating the growth of droplets very rapidly bypicking up more droplets. This process promotes the collection ofcondensed moisture on SLIPS coated surfaces before they go back toatmosphere by evaporation.

The biggest disadvantage of spin coating is the lack of materialefficiency. Only 2-5% of total dispensed materials are used while therest goes to the surface of coating bowl and disposed. Not only the costof the material itself (e.g. photoresist used in semiconductor industry)is gradually increasing but also the cost for properly disposing ofthese materials are increasing. The materials used as the body of spincoaters are generally metals or plastics that can be easily coated withSLIPS, such as boehmite coating. This specific application does notrequire optical clarity nor mechanical durability. A possible product isin the form of either SLIPS-coated spin coater or SLIPS-coatedliners/sleeves that the users can attach and replace when needed. Thecollected materials should be able to be reused and to reduce the costof production of semiconductor devices.

Example 8 SLIPS Surfaces for Anti-Graffiti

A surface was partly treated with SLIPS and adherence of paint andstickers were tested. As shown in FIG. 21, SLIPS treated surfaces werehighly resistant to spray paint as whereas surfaces that were nottreated with SLIPS were not able to repel the spray paint. As shown inFIG. 22, SLIPS treated surfaces were highly resistant to stickers wherethe stickers were extremely easy to remove and left no residue. Incontrast, the stickers adhered strongly to surfaces that were nottreated with SLIPS and left residue when removed. Hence, SLIPS surfacecan be utilized as anti-graffiti signs.

Example 9 SLIPS Assembled by Layer-by-Layer Deposition Process

In this example, a layer-by-layer process to alternately assemblepositively charged polyelectrolytes and negatively charged silicananoparticles onto a given substrate is utilized. Surface modificationof the particles by silane chemistry and infusion of a lubricant withmatching chemical composition creates a stable substrate/lubricantinterface that repels any immiscible second liquid. The coating protocoluses adsorption from aqueous solutions and is thus environmentallybenign and can be applied to arbitrary surfaces, given that they can bebrought in contact with water. The process is completely scalable andcan be readily automated.

FIG. 23A schematically shows the fabrication of the surface coating.Negative charges are introduced to the substrate (i) and subsequentlayers of positively charged polyelectrolyte (ii) and negative chargedsilica nanoparticles (iii) are adsorbed to form a hybrid thin film (iv)that can but not necessarily has to be calcined to produce a poroussilica coating (v). After fluorosilanization (vi), a fluorinatedlubricant is wicked into the coating (vii) and will not be displaced bya second, immiscible liquid that slides off the substrate with ease(viii).

In certain embodiments, negative charges are created on the substrate byplasma treatment, UV-ozone or immersion in base piranha. The substrateis subsequently immersed into a solution of positively chargedpolyelectrolyte (poly-diallyldimethyl ammonium chloride, PDADMAC),rinsed and immersed into a solution of negatively charged Ludox™ silicananoparticles. Electrostatic attraction leads to the formation of afuzzy, disordered film of polymer and nanoparticles. The assembledhybrid film is calcined or plasma treated to remove the polymer andleave a disordered, porous silica nanoparticle assembly on thesubstrate, the surface of which is subsequently silanized with1H,1H,2H,2H-(tridecafluorooctyl)-trichlorosilane to introducefluorinated surface functionalities. A fluorinated lubricant oil (DuPontKrytox™ 100), matching the surface chemistry of the coating, isinfiltrated into the porous structure. The matching surface chemistrybetween surface structures and lubricant creates a strong affinity andleads to a minimization of the total surface energy for asolid/lubricant/liquid system in which a second, immiscible liquid isnot in contact with the solid substrate. If this criterion is fulfilled,the lubricant layer will not be displaced by other liquids and thusenable a highly efficient repellency of various, immiscible liquids byelimination of pinning points.

Any other combination of surface chemistry and lubrication can be usedas well; including but not limited to alkyl-silanes with hydrocarbonoils, olive oil, sunflower oil, etc.; pegylated or hydrophilic silaneswith water or ethylene glycol, and the like.

SEM images of the silica nanoparticle coating prepared with differentdeposition cycles taken after calcination are shown in FIG. 23B. Anincrease in particle number and film density with increasing depositioncycles is visible. Quartz Crystal Microbalance (QCM) measurementsfurther show evidence of a constant addition of silica nanoparticleswith each deposition cycle after the first two cycles (FIGS. 24A and24B). This allows for a precise adjustment of the total roughness andthickness of the coating. UV-Vis-NIR transmittance measurements of thelubricated substrates show an increase in light transmittance throughoutthe visible spectrum compared to a reference glass slide for all coatedsubstrates (FIG. 24C). A slight increase in transmittance withincreasing number of layers is detected which is attributed to anincrease in surface roughness leading to a more diffuse interface thatreduces the reflection of light.

The repellent properties of the coatings with varying numbers ofdeposited layers were quantified by contact angle and sliding anglemeasurements using water and octane as test liquids. With increasinglayer thickness, the static water contact angle after fluorosilanizationsteadily increased and leveled at 120° for 4 or more deposition cycles,indicating a complete coverage of the surface with silica nanoparticles.Thus, the dry coating does not possess superhydrophobic properties dueto the extremely small size of the silica nanoparticles and the absenceof hierarchical superstructures. As a consequence, a droplet of waterplaced on a coated surface experiences strong pinning and slides of onlyafter tilting to very high substrate angles (FIG. 25A, light graycolumns). Similarly, an octane droplet is pinned but, due to its lowersurface tension it starts moving at approximately 350 (FIG. 25B).However, it leaves a stained surface behind. The addition of lubricanthas strong effects on the repellency properties. The absence of pinningpoints for the liquid residing on top of the lubricant layer leads tohighly efficient repellency with extremely low contact angle hysteresisand sliding angles of approximately 2° for both water and octane (FIGS.25A-25B). FIGS. 25C and 25D exemplarily show the highly efficientremoval of a droplet of water and octane on a lubricated substratetilted at an angle of 2° coated with 5 layers of silica nanoparticles.Effective liquid repellency, characterized by a sliding angle droppingbelow 5° is achieved for coatings with at least 3 (octane) or 4 layers(water) (FIGS. 25A-25B). The low sliding angle, hinting at the absenceof pinning points, indicates that the surface roughness in coatings from3 or more deposition cycles is sufficient to enable stable repellency asthe lubricant film is not displaced by the liquid to be repelled.

The solution-based assembly method allows for the coating of arbitrarilyshaped surfaces. In FIGS. 26A-26D, time-lapsed images that demonstratethe efficient repellency of honey from the inside of a coated glass vial(FIG. 26A, lower row) and of crude oil from the inside of a glass tube(FIG. 26B, lower row) are shown, visualized by clear sliding of thefluid without getting stuck to the surface. Honey and crude oil werechosen as examples of extremely sticky complex fluids that cannot beremoved from uncoated surfaces (FIGS. 26A-26B, upper row). Similarly,other complex fluids (PMMA solution in dimethylformamide, mustard) areeasily repelled from arbitrarily-shaped glass objects such as chemicalflasks and highly curved test-tube surfaces. The layer-by-layerdeposition process can be applied to a large variety of substratematerials. The only requirement for the process is the possibility tocreate charges on the substrate surface, which can be achieved by avariety of methods, including treating the substrates with oxygenplasma, UV-ozone, acid or base piranha or a corona discharger. Thetreatment time can be chosen to be short enough not to degrade thesubstrate material since a very short exposure is sufficient to create acharged interface. FIGS. 26C and 26D exemplarily demonstrate thesuccessful assembly of the omniphobic, highly repellent layer-by-layersilica nanoparticle coating on a metal (stainless steel) and a polymersubstrate (poly methylmethacrylate) by showing the sliding of a stainedoctane droplet under an angle of 15° without leaving traces on thesurface. Untreated substrates were completely stained by the sametreatment (FIGS. 26C and 26D, upper row). Further examples ofsuccessfully coated surfaces, include aluminum, poly propylene andpolysulfone.

Table 3 quantifies the wetting behavior of all tested substrates bycomparing the sliding angles of water and octane for uncoated samples,fluorosilanized layer-by-layer silica nanoparticle coatings and the samecoatings after addition of lubricant. All uncoated samples failed toremove water as the droplets remained pinned even after tilting thesubstrate to 90° and were wetted and stained by octane. The introductionof the surface coating changed the wetting properties consistently forall samples but showed high contact angle hysteresis and sliding anglesfor both liquids. The presence of octane stains on the surfacesindicated the failure of the dry coating in repelling the liquid. Allcoated, lubricated samples showed extremely small sliding angles,contact angle hysteresis and absence of staining, thus demonstrating thehighly efficient repellency of water and octane as an example of a lowsurface tension liquid.

TABLE 3 Sliding angles of octane and water on different substratescoated with a layer-by-layer silica nanoparticles coating (7 depositedlayers). Water sliding angle/° Octane sliding angle/° Lubri- Lubri-Substrate Un- Dry cated Un- Dry cated Material coated coating coatingcoated coating* coating** Glass 56 ± 8 66 ± 5 2 ± 1 16 ± 3 31 ± 3 2 ± 1Aluminum pinned 63 ± 4 2 ± 1 wetted  51 ± 13 2 ± 1 Stainless pinned 85 ±5 1 ± 1 wetted 49 ± 7 1 ± 1 Steel PMMA pinned pinned 2 ± 1 wetted 46 ± 52 ± 1 PP pinned pinned 1 ± 1 wetted 48 ± 6 2 ± 1 PSu pinned pinned 2 ± 1wetted 44 ± 5 2 ± 1 *octane droplet left stains on the surface aftersliding **no contamination of the surface alter sliding

In conclusion, a simple coating to introduce efficient liquid repellencyhas been demonstrated to a wide variety of materials with completelyarbitrary shapes. The surface structure is prepared by a layer-by-layerdeposition of positively charged polyelectrolytes and negatively chargedsilica nanoparticles. After fluorosilanization of the silicananoparticles, a fluorinated lubricant is infiltrated into the porouscoating and firmly held in place by matching surface chemistry. Thestrong affinity of the lubricant to the substrate prevents a secondliquid from getting into contact with the substrate and resides on topof the lubricant layer, whose fluid nature gives rises to an extremelysmooth interface without pinning points. Therefore, the liquid slidesoff the substrate with ease. The small size of the silica nanoparticlesapplied in the process does not interfere with light of visiblewavelengths and, thus, gives rise to a completely transparent coating.Successful repellency of water, octane as a low surface tension liquidand various complex fluids on a variety of arbitrarily shaped ceramic,metal and polymer surfaces has been demonstrated. The deposition processis conceptually simple, of low cost, based on aqueous solvents and thusenvironmentally benign, completely scalable and readily automatable. Thepresented method thus combines all the remarkable properties ofpreviously reported liquid infused coatings with an unprecedented degreeof simplicity and versatility with respect to accessible substratematerials, shapes and sizes.

Example 10 SLIPS Assembled by Layer-by-Layer Deposition Process OverPDMS Substrate

PDMS is a material widely used in medical equipment, for example incatheters. Also, it is the material of choice for microfluidictechnologies. Therefore, repellent coatings on PDMS are of relevance. Alayer-by-layer adsorption process was applied on PDMS that was oxygenplasma treated for 1 minute to induce negative surface charges. Thelayer-by-layer assembly technique shown in FIG. 23A was utilized to formSLIPS surfaces.

Contact angle hysteresis and sliding angle (20 μl) measurements of waterand hexadecane confirm the presence of a repellent coating, as shown inFIGS. 27A-27D.

In addition, the effect of strain (0% to 20%) on the retention of theslippery nature of layer-by-layer coated, lubricant infiltrated PDMSwith 0 layers (reference, top) and 9 layers (bottom) are compared inFIG. 28. As shown, the slippery properties are retained with significantamounts of strain.

Example 11 SLIPS from Sol-Gel Derived Nanoporous Boehmite NanofiberPaper

Another potential class of SLIPS substrate is based on free-standingnanoporous films/membranes using high-aspect-ratio bohemite nanofibers.High-aspect-ratio boehmite nanofibers can be prepared using asolvothermal synthesis.

FIGS. 29A-29D show SEM images of such a porous “paper” produced fromboehmite nanofibers. As shown, the boehmite nanofibers tend to align.

Example 12 Free Standing Boehmite Films

In an experiment similar to Example 11, 6.8 g of aluminum isopropoxide(precursor) is added dropwise to 60 mL of water heated to 75° C. tomaximize the hydrolysis of the precursor. If precursor is added too fastthere is potential for premature self-condensation of the particlesresulting in the formation of agglomerated chunks rather than fibers.Once the entire precursor is added, the solution is heated to 90° C. toallow the vaporization of isopropyl alcohol (byproduct of the reaction).The hot solution is then transferred to a Teflon-lined stainless steelpressure vessel and 0.61 g of glacial acetic acid is slowly added to thesolution with stirring to lower the pH to ˜3. The acetic acid increasesthe rate of hydrolysis of the precursor in addition to promotingunidirectional growth of boehmite along one plane of the particles. Theautoclave is heated to 150° C. for 6-24 h. The time of the reactiondirectly correlates to the length of the nanofibers obtained, longerreaction time results in longer nanofibers. TEM characterization wasperformed on a drop cast sample of the resultant solution to determinethe aspect ratio of nanofibers.

The resulting solution from the reaction is diluted to approximately 2.8wt. % nanofibers and 1 wt. % polyvinyl alcohol (3000-4000 MW) is added.The mixture is sonicated for 30 min and the resulting solution isdegassed under vacuum. The solution is cast in a Teflon-lined dish andslowly dried in an oven at 40° C. for 48-72 h. The resultingfree-standing boehmite nanofiber film can be gently peeled off of thedish. FIG. 29E shows a TEM image of individual solvothermal boehmitenanofibers with some agglomerated particles. FIG. 29F shows SEM image ofbundled boehmite nanofibers drop cast on a copper conductive tape.

The film thickness can be adjusted by modifying the concentration ofbohemite nanofibers and polyvinyl alcohol.

Modification of the standard SLIPS procedure via alumina sol-gel routecan be successfully altered to produce comparable surfaces with agreater range of application methods.

Example 13 Carbon Nanofiber—Epoxy Surfaces for SLIPS Applications

Epoxy EPON 862 and curing agent EPIKURE W were purchased fromMiller-Stephenson, carbon nanofibers, graphitized (iron-free) werepurchased from Sigma-Aldrich, and acetone was purchased fromSigma-Aldrich.

The epoxy-based carbon nanotube composites were fabricated by immersingthe MW-CNT fibers into an acetone for 30 min in ultrasonic bath, thensolution of Epon 862 epoxy was added to the mixture CNT/Acetone. Acetonereduces viscosity of the epoxy making it possible to better dispersionof CNTs. Solution of CNT-Acetone/Epon 862 was gradually heated to 70° C.under vigorous stirring to remove residue of acetone, than Epikurecuring agent W was added in the ratio of 100:25 to the Epon 862 andstirred for additional 30 min. Degassing is performed under vacuum toremove the bubbles generated during mixing. Samples were cured in vacuumoven at 70° C. for 48 h. Plasma etching was used to etch epoxy matrix.

FIGS. 30A and 30B show a (A) top view and (B) cross section HR-SEMimages of multi wall carbon nanotubes dispersed in epoxy resin matrixprior plasma etching. Scale bars are 200 nm. Samples were spattered with3 nm Pt/Pd alloy prior to image acquisition.

Example 14 Superhydrophobic Alumina Nanoparticles and theirNanocomposites

Nanoporous surfaces for fabricating SLIPS can be prepared usingmaterials with inherently robust mechanical properties. FIG. 31A showsan exemplary method to generate surface functionalized aluminananoparticles (AlNPs) for use as filler material in nanocomposites, sothat hydrophobicity is achieved that is sufficient for forming robustSLIPS.

As shown in FIG. 31A, AlNPs naturally have a native oxide layer which isneutral. However, for surface modification using compounds such asorganophosphonic acids and organophosphate esters, high density ofsurface hydroxyl groups is required. As shown in Step 1 of FIG. 31A,this is achieved by applying Fenton chemistry (Iron catalyzed mildpiranha solution) with stirring in a 4:1 ratio of H₂SO₄ (0.1 M): H₂O₂(30%) for extended periods of time.

FIG. 31B shows the normalized FTIR absorbance spectra of O—H stretchingmode recorded from AlNPs taken at different treatment times with Fentonchemistry. The ‘X’ indicates no modification and ‘XOH’ indicates surfacemodification using O₂ plasma treatment.

Next, as shown in Step 2 of FIG. 31A, the hydroxylated AlNPs are chargedinto FS100 solution with zirconia grinding dispersion media and rotatedon a ball mill. This maximizes de-agglomeration and surface modificationof the particles. Post modification, the AlNPs are retrieved bycentrifugation and are rinsed with ethanol at least three times toremove any excess surfactant. Excess solvent is evaporated from theparticles at 70° C. and in the presence of vacuum.

Surface functionalized AlNPs can now be re-dispersed in compatiblesolvents such as hydrofluoroether (HFE) or 2,2,2-trifluoroethanol (TFE).The resulting dispersions can be used to cast films onto oxygen plasmatreated glass substrates and the solvent is evaporated at elevatedtemperatures. To permanently bind particles to substrates, 1) theparticle can be modified with mixed ligands (e.g. fluorinated andacrylate), 2) epoxy, polyurethane or a similar binding agent is used. Todecrease the viscosity of the epoxy resin, acetone is added in 5:1 w/wratio and the resulting solution is sonicated until it forms ahomogeneous mixture. The curing agent is then added in a 4:1 w/w ratioand is sonicated for 30 min. The functionalized AlNPs are then uniformlycoated over the epoxy and placed at 70° C. in an oven for 48 h to fullycure the epoxy resin. Initial qualitative observations showed resultingsurface to be superhydrophobic to support SLIPS and much moremechanically robust than compared to conventional alumina sol-gelcoating. On the other hand the AlNPs can be used as a filler material ina curable nanocomposite with varying volume fractions and subsequentlybe applied to surfaces to form nanoporous films to support SLIPS.

Functionalized AlNPs in epoxy composite provide an alternative toalumina sol-gel coated substrates with increased mechanical properties.

Example 15 Fabrics Coated with Lubricated Nanostructures DisplayingRobust Omniphobicity

The development of a stain-resistant and pressure-stable textile isdesirable for consumer and industrial applications alike, yet it remainsa challenge that current technologies have been unable to fully address.Herein the rational design and optimization of nanostructuredlubricant-infused fabrics are presented. The improved fabricsdemonstrate markedly improved performance over traditionalsuperhydrophobic (TSH) textile treatments: SLIPS-functionalized cottonand polyester fabrics exhibit decreased contact angle hysteresis andsliding angles, omnirepellent properties against various fluidsincluding polar and nonpolar liquids, pressure tolerance and mechanicalrobustness, all of which are not readily achievable with thestate-of-the-art superhydrophobic coatings.

As shown in FIG. 32, two methods were developed to create nanoscalesurface roughness: I) coating the textile fibers with silicamicro-particles (SiM), and II) boehmite nanostructure formation on thetextile fibers from sol-gel alumina treatment (SgB). As shown, a single,bare fiber being functionalized with SLIPS is depicted in a schematic(A-D). A bare fiber (A) is roughened with the silica micro-particle(SiM) or sol-gel boehmite (SgB) approach (B) and fluorinated to achievechemical similarity to (perfluoroether) polymer Krytox (C) before thelubricating film is applied (D). This confers pressure-tolerant,self-healing repellency against a broad range of fluids. The flow chart(E) contains more specific information regarding the SiM and SgBfunctionalization protocols applied to cotton and polyester fabrics.Upon fluorination and subsequent infiltration with the lubricant,SLIPS-fabric can be produced from either approach.

The two surface modification methods were applied to seven differenttypes of fabric samples—two cotton and five polyester (PE)—and thenonwetting performance was evaluated by quantifying static contactangle, contact angle hysteresis, liquid repellency after mechanicalstress, pressure tolerance, and breathability. The characterizationherein provides strong evidence that SLIPS-fabrics exhibit uniquecombination of liquid repellency, durability, and pressure-tolerancethat are difficult to achieve based on state-of-the-art traditionalsuperhydrophobic materials.

The Dense polyester was purchased from Sew-Lew Fabrics, Cambridge,Mass., the microfiber polyester was purchased from MicroFibres, Inc. andthe Nike polyester was cut from Nike Dri-Fit 100% polyester runningshorts purchased from City Sports, Cambridge, Mass. The rest of thefabrics were purchased from nearby fabric stores, including Sew-Lew inCambridge, Mass. and Winmill Fabrics in Boston, Mass. With regard toterminology, “fibers” are twisted together to makes “threads”, which arein turn woven to make the fabric. The polyester fabrics were treatedbefore silica micro-bead deposition. Amines readily react with polyesterby nucleophillic acyl cleavage of the ester linkages for surfaceactivation. Five to eight 2×2 cm squares of polyester were first cleanedwith DI water, ethanol, and then hexane. Fabrics were dried for at least1 h at 70° C. and further dried with a heat gun before adding to a 1%solution of aminopropyltriethoxysilane (APTES, Sigma Aldrich) inanhydrous toluene (Sigma Aldrich) and stirring for 24 h at 65° C. underdry nitrogen. Samples were then removed, rinsed with toluene severaltimes, and dried under vacuum. Dried samples were submerged in deionizedwater overnight, removed, rinsed with water, and dried for at least 3 hunder vacuum before immersing in a 1% tetraethyl orthosilicate (TEOS)solution in water for 4-8 h. Samples were rinsed with water and driedovernight before silica particle deposition.

In-situ polymerization of silica-microparticles onto cotton or activatedpolyester was performed to obtain a roughened substrate for SLIPS.Jersey cotton and Muslin were cleaned with water, ethanol, and isopropylalcohol prior to reaction. The prepared samples were submerged into a1:3 mixture of methanol and isopropanol, 20 mL ammonium hydroxide (SigmaAldrich, St. Louis Mo.), and 12 mL TEOS (Sigma Aldrich, St. Louis Mo.).All solvents and chemicals were used without further modification. Themixture was stirred for 6 h at room temperature, and the samples wereisolated and rinsed extensively with toluene several times. Driedfabrics were blown with compressed air to remove any residual detachedparticles that were not firmly attached to the fabric fibers. Subsequentfluorosilanization renders the fabric surface superhydrophobic.

The roughened silica-bead surface was fluorosilanized either with1H,1H,2H,2Hperfluorooctyltriethoxysilane (Sigma-Aldrich) orperfluorododecyl-1H,1H,2H,2H-triethoxysilane (Gelest). A solution of4.8% silane stock and >99.7% acetic acid were mixed in equal parts in200 proof ethanol (i.e., in a 1:1:19 ratio of the above ingredients).After this, mixture was stirred for 60 min (to allow sufficientoligomerization), the fabrics were dipped into the mixture for 2-4 minand allowed to hang dry. The silane chains attach to the surface of thesilica coating of the fabric and render the rough surfacesuperhydrophobic. Silica-microparticle (SiM) deposition is an effectivemethod used to confer microscale surface roughness on cotton fabrics.FIG. 33 summarizes the steps for this scalable process. Fewer steps maybe needed to achieve the desired surface treatment for chemicallyreactive, hydroxyl-rich cotton fabrics. To induce covalent adherence ofsilica particles to more inert polyesters, a two-step surface activationprocess was utilized whereby polyester cleavage using(3-aminopropyl)triethoxysilane (APTES) and subsequent reaction with TEOScreated silica-like surface functionalities. Chemical composition ofeach fabric surface was confirmed using FTIR. Once silica-like surfacechemistry was achieved, uniform particles were synthesized within allfabric samples to ultimately form a rough, nanostructured surface.Lastly, fabrics were dipped into an perfluoroalkyl-silane/ethanolsolution to render the rough surface superhydrophobic, thus completingthe SiM functionalization.

All cotton and polyester samples were oxygen plasma cleaned for 300 s(250 watts, oxygen flow of 15 cm3/min). Cleaned samples were dipped inalumina sol-gel pre-cursor. After 10 min, the fabric was removed anddried overnight at 70° C. Dried samples were immersed in a 95° C. waterbath for 15 min to create boehmite nanostructures, removed, dried, andthen submerged in a 1% solution of FS-100, a perfluoroalkyl phosphatesurfactant (Mason Chemical Company), in ethanol (Chemguard Inc.,Mansfield, Tex., USA) for 1 h at 70° C. Samples were rinsed with ethanoland dried overnight before performing the contact angle and SEManalyses. Boehmite, formed in a reaction between aluminum and 80-100° C.water, is a dense network of nano-scale AlO(OH) crossed leaflets thatcan be fluorinated to become an effective superhydrophobic surface. Thesol-gel approach schematically shown in FIG. 33 was utilized to coatfabrics with boehmite nanostructures.

The surface of SgB or SiM functionalized samples has a strong affinityto fluorinated oils. To avoid excessive lubrication, perfluoropolyetherlubricant Krytox™ (Dupont Inc.) was applied to wick through the sampleand the excess was removed by contacting the surface of the sample witha Kimwipe. About 30-100 μL of oil infused 4 cm2 of the material,depending on the fabric thickness.

SEM characterization was performed with a Zeiss Supra field emissionmicroscope. Samples were coated by Pt—Pd sputtering for 60-150 s priorto SEM characterization.

Contact angles were recoded using a contact angle goniometer (CAM 101,KSV Instruments, resolution=0.01 o) at room temperature. 10 μL dropletsof DI water were used for all static contact angle measurements. Contactangle hysteresis (CAH) values were obtained by slowly increasing anddecreasing droplet volume using a syringe needle while imaging thedroplet movement, measuring advancing and receding contact angles,respectively, from these images, and subtracting the averages of thesevalues. At least seven independent measurements were taken for static,advancing, and receding contact angles.

For a twisting test, a 2×3 cm SiM or SgB fabric sample was securedbetween two medium sized clamp-type paper clips, and the assembly washung by affixing one of the clips to a hook. By rotating the unboundlower clip, the fabrics were twisted ±360°; the first twist was definedas a 360° rotation clockwise followed by a return to rest position, thesecond twist was 360° counterclockwise followed by a return to restposition, and so on. After the specified number of twists (0, 5, or 50),the sliding angle of a 20 μL droplet of DI water was measured at least 3times. The sliding angle is the tilting angle at which the dropletbegins to slide along the surface without pinning. The sliding angledata and the SEM characterization provide a complete picture of theperformance deterioration resulting from the twisting test.

A SgB or SiM fabric sample was secured to a surface with tape andvigorously rubbed with a rolled up Kimwipe for approximately 10 s. Thisis a preliminary abrasion test that simulates a contact with otherfabrics or the surrounding environment. Damage was qualitativelyobserved by testing the repellency of water before and after rubbing,and SEM characterization showed the physical damage occurring to thenanostructure.

The American Association of Textile Chemists and Colorists (AATCC) test#193 was used to analyze the repellency of non-lubricated (TSH) andlubricated (SLIPS) fabric samples to low surface-tension aqueous testliquids. Eight test liquids, composed of different volume fractions ofIPA in de-ionized water, were prepared. Beginning with the highestsurface tension liquid, a test droplet was applied to the surface of thefabric sample and allowed to sit for 30 s. The droplet was then observedto assess the wetting of the fabric: if the fabric is not wetted, thenthe process is repeated for the next test liquid, and if the surface iswetted then the fabric receives a score corresponding to the previouslyapplied test liquid (i.e., the lowest surface tension liquid repelled bythe fabric). If the test liquid only slightly wets the surface, thefabric is assigned a non-integer score halfway between the previous andcurrent test liquid. A maximum score of 8 may be achieved, if the sampleis not wetted by any of the test liquids.

The AATCC test #188 was used to test repellency against alkanes ofdecreasing surface tension to characterize the repellency of oils andother nonpolar liquids. This test is very similar to the aqueous liquidrepellency test: the droplets were placed on TSH and SLIPS samples for10 s before the wetting behavior was observed. Again, the lowest surfacetension liquid that does not wet the surface of the liquid determinesthe score. Non-integer scores may be assigned, if only partial wettingoccurs, and a maximum score of 8 is achieved when even test liquid 8,the lowest surface tension liquid in the test, does not wet the surfaceof the fabric.

The tolerance of fabric samples to pressurized liquids of high and lowsurface tension was measured with the droplet impact test. A pipette wasfixed 20.3±0.5 cm above a fabric sample immobilized on a tilting stagewith double-sided tape. A 10 μL test droplet was carefully ejected fromthe pipette and impacted the surface of the fabric at a controlledvelocity, and the sliding angle of the droplet was measured immediatelyafter impact. The dynamic pressure was estimated by P_(dynamic)=½ρV²,where ρ is the density of the liquid and V is the impacting velocity.The impact velocity was estimated using kinematic equations, and thusthe tetradecane droplet exerts a dynamic pressure of ˜1520 Pa and thewater droplet exerts a dynamic pressure of ˜1990 Pa. Irreversiblepinning occurs for the superhydrophobic samples and cannot be recorded;the most important information comes from whether the droplet slides ordoes not slide.

The breathability test was adapted from the standard ASTM E96-E uprightcup water vapor transmission test. Each fabric sample was tested by asingle 3D printed capsule; the inside of the capsule was dried by 20 gof Drierite desiccant (Drierite, Inc., Xenia Ohio) and separated fromthe moist air outside of the capsule by the fabric sample that wassealed onto the capsule by a ring-shaped cap clamped in place. Inbetween repeated experiments, the desiccant was regenerated by placinginto a vacuum oven at ˜150° C. overnight. The external environment ofthe chambers was carefully controlled in a custom made environmentalchamber maintained at 50% relative humidity and 23±1° C. Minimal airflowin the chamber prevented temperature gradients and inconsistencies. Thewater vapor was pulled into the chamber through the sample by thehumidity gradient. After initial weighing, the test capsules wereremoved from the environmental chamber and weighed after 1, 2, 3, 4, 5,6, 8, 22, 24 h, and the mass increase of each chamber was plotted (FIGS.6 and 7). To confirm the omniphobicity, sliding angles of hexadecaneand/or de-ionized water droplets on lubricated samples were recorded.The mass of the lubricated membranes (and thus the mass of thelubricant) before and after 24 h was also recorded. A typical experimentincluded up to 9 capsules running simultaneously. In each experiment,two controls were always present to ensure consistency in conditionsbetween experiments: an open chamber without a membrane and a chambersealed by Parafilm, which is impermeable to water vapor (PechineyPlastic Company, Chicago, Ill.). Lubricated and untreated samples weretested against each other to observe the effect of SLIPS on thebreathability of the fabric. Each sample was tested a minimum of threetimes, either with three separate samples in a single experiment or withone sample across three separate experiments.

Fabrics introduce unique physical features (hierarchical feature sizescoming from fiber-thread-weave length scales), logistical considerations(cost, complexity of procedure), and demanding applications (requiringdurability, breathability, etc.) into the design space of the finalmaterial. Cotton and polyester (PE) are inexpensive, readily available,widely used, and environmentally friendly. The weave of the fabric is animportant parameter since it inherently has a much more complextopography than a simple, flat surface. There are textiles available ofmyriad thread sizes, weave densities, and weave patterns; the effect ofthese parameters on the quality of the SLIPS coating is unknown andneeds to be investigated.

A very common weave pattern is a basic, square-type weave. Since this isa relatively simple system, a number of different square-weave fabricswere selected—Dense PE, Nike PE, Crepe PE, and Muslin Cotton (M.Cotton)—with weave densities ranging from very high (tightly woven) tovery low (loosely woven with larger spaces present) to investigate therole of this parameter in developing effective omniphobic SLIPS-fabrics.Three fabrics of different weave patterns were also tested, includingthe randomly oriented microfiber (μfiber) threads, the V-shaped weave ofGavadeen PE (Gay), and the column-based weave of the Jersey Cotton (J.Cotton) (see FIG. 33). As shown in FIG. 33, the square-weave fabrics arearranged along the top row (A-D) in order of decreasing weave density,and the fabrics of other weaves are arranged along the bottom row (E-G).The two cotton fabrics are on the right edge of the figure (D, G). DensePolyester (PE) (A) showcases a tight, squaretype weave with threads ˜150μm across, resulting in a virtually flat surface free of loose fibers.Nike PE (B) exhibits a looser square-type weave and is comprised ofthreads ˜200 μm across. Crepe PE (C) is the most loosely wovensquare-type PE fabric, with fibers ˜300 μm across. Muslin Cotton (D) isthe least densely woven square-type fabric, with vertically orientedthreads ˜350 μm in diameter, horizontally oriented threads ˜250 μm indiameter, and large gaps in between thread intersections. Note thepresence of loose threads on this sample. Gavadeen PE (E) displays aV-type weave comprised of threads ˜300 μm across; the vertically alignedfibers in the image are comprised of smaller fibers while thehorizontally aligned threads are comprised of larger fibers, resultingin a diagonally ridged structure. μfiber (F) has small fibers ˜5 μm indiameter that create a disordered, “hairy” structure. Jersey Cotton (G)consists of an entangled weave of spaciously woven threads ˜200 μmacross; many loose threads are present.

SiM and SgB treatment and surface fluorination according to theprocedure outlined in FIG. 32, resulted in fabrics uniformly coveredwith silica micro-particles (˜150-500 nm in diameter) or boehmitenanoflakes, respectively. As shown in FIG. 34, a scanning electronmicroscope was used to evaluate the surface roughness and durability ofthe sol-gel boehmite (SgB) (A-D) and silica microparticle (SiM) (E-H)treatments on Nike polyester fabric. All scale bars are 2 μm. Freshlytreated SgB fibers (A) show full coverage of the fiber with SgB;dramatic microbead coverage is apparent on freshly treated SiM fibers(E). High magnification of the microstructures (B, F) reveals thesurface roughness that facilitates good SLIPS performance. When twisted50 times, smoother boehmite is still present (C) in crevices betweenfibers, while the outside of the fibers have become smooth. Also after50 twists, the SiM threads (G) exhibit some cracking while maintaininggood microparticle coverage. After vigorous rubbing with a Kimwipe, SgBfabric (D) exhibits cracking and smoothness on the outer fibers, whileunder the same conditions the SiM coating remains intact (H).

Droplets bounce off the surface of these fabrics and static contactangles characteristic of superhydrophobic surfaces (>150°) were observed(see FIG. 35A). SiM- and SgB-treated fabrics were then infused with aperfluoropolyether lubricant (Krytox™. DuPont) that remains stablyanchored in the textured substrate. These SLIPS-fabrics show anunprecedented ability to repel a wide range of fluids and to beresistant to staining. To determine the optimal SLIPS fabric parameters,the static contact angle, contact angle hysteresis, pressure resistance,durability, and breathability were investigated. Three phases of testingon a successively smaller set of samples were investigated as shown inthe Table 4 below.

TABLE 4 Abbre- Phase I Phase II Phase III Fabric Name viation SgB SiMSgB SiM SgB SiM Muslin Cotton M. Cotton * * * * * Jersey Cotton J.Cotton * * * Dense Polyester Dense PE * * * * Nike Polyester NikePE * * * * * Microfiber μfiber * * * * Polyester Gavadeen Gav. * * *Polyester Crepe Polyester Crepe * * *

To begin Phase I characterization, the static contact angle weremeasured on all fabrics to quantify the hydrophobicity of non-lubricated(TSH) and lubricated (SLIPS) samples. Fabric samples, both un-lubricatedand lubricated with Krytox 102 (K102), were functionalized with eithersilica microbeads (SiM) or sol-gel boehmite (SgB). Contact angles weremeasured using a contact angle goniometer. As shown in FIG. 35A, a 10 μLwater droplet was placed onto the surface of the fabric sample formeasurement. FIG. 35B shows the advancing and receding contact anglesthat were recorded and these values were subtracted to determine thehysteresis. N=7; error bars are +/−SD. Asterisks denote statisticallysignificant results (Student's two-tailed t-test, P<0.05); comparisonsare only made between SiM+K102 and SgB+K102 for each fabric sample. Asshown, each non-lubricated sample has a static contact angle in therange of 150-160°, and when the Krytox lubricating film is applied thisangle decreases to approximately 110-120°. To quantify the repellency ofthe fabrics, the contact angle hysteresis (CAH), which is the differencebetween advancing and receding contact angles as a droplet slides on asurface and directly relates to droplet mobility on a surface, wasmeasured. Low CAH was observed on almost all SLIPSfabric samples. FIG.35B shows all CAH data for the 14 fabric samples. In the case ofnon-lubricated fabrics, there are multiple sources of pinning, includingfibrillar protrusions, structural defects, and perhaps incompletefluorination leaving hydrophilic areas on the surface. CAH valuesincrease with increasing density of defects, or pinning points, on thesurface of the material. Application of a lubricant dramatically reduceshysteresis for every fabric sample except for J. Cotton and CrepePE—droplets easily slide over the smooth surface created by thelubricating film. In the case of Gavadeen PE treated with SiM-SLIPS,which has a static contact angle of 156.6°±3.1 and a hysteresis value of5.35°±0 3.1, a combination of superhydrophobic and SLIPS-typeperformance was observed. It appears that the lubricant entrapped withinand around each nanostructured thread prevents pinning even if the testliquid is partially exposed to the non-lubricated, superhydrophobicsurface, a scenario suggested by a relatively high static contact angleand a relatively low hysteresis value. Thus, fabrics that combineslippery performance with both SLIPS and TSH attributes have beenproduced for excellent overall water repellency.

Reducing the sample pool with the selection criteria discussed earlier(Table 5), tests were carried to determine which treatment method—SgB orSiM—is more robust when subjected to rubbing and twisting, as observedby the effect of twisting on sliding angle and coating integrity asstudied by SEM. These experiments simulate the expected wear thatfabrics may experience in most functional applications.

The twist testing data are shown in FIG. 36. The fabric samples weretwisted +/−360° with a custom-made setup, and the sliding angle of water(20 μL droplet volume) on a fabric sample lubricated with Krytox 102 wasmeasured after 0, 5, and 50 twists. Sliding angles that exceeded 35° areindicated on FIG. 36 as being 35° with arrows (̂) because of experimentalconstraints and the large variability associated with strong pinningbehaviors. Notably, the test water droplet did not wet any of the fabricsamples after twisting 50 times. Remarkably, even when pinning wasobserved, the colored test water droplets could be rinsed away withoutleaving a stain.

SgB Gav. and SgB M. Cotton were the worst performers in the twistingtest: both fabrics failed to slide at 35° even before twisting, and itwas qualitatively observed that droplet pinning worsens with furthertwisting. For those samples whose sliding angles remain less than 35°, aclear difference emerged between the SgB samples and the SiM samples:for the SgB-treated samples, there is a significant increase in thesliding angle for 0, 5, and 50 twists, while on the SiM treated samplesthere is either no significant increase, or an initial increase thatstabilizes with additional twisting. The most telling result comes fromcomparing SgB Nike PE with the SiM variant: the SgB sample shows aclear, almost linear increase in the sliding angle with increased numberof twists, while the SiM sample shows no significant change.

An increase in sliding angle indicates that damaged nanostructures giverise to a decreased affinity of the lubricant to the fiber surfaceeither due to the loss of nanostructure or due to cracks exposingsurfaces that are not fluorinated. SiM fabrics exhibit more durablenanostructures than SgB fabrics. SEM images of the Nike PE fabrictreated with both SgB and SiM, before and after twisting, confirm this(see FIG. 34). The SiM layer on the Nike PE fabric showed only minimaldamage after 50 twists, whereas the boehmite shows smoothening andflattening of its nanostructures. Self-healing behavior arises in SLIPSfrom a redistribution of the lubricant to cover moderate damage and tocontinue to provide omniphobicity. In this way, the liquid-repellentperformance of SLIPS-fabrics is less susceptible to damage than that ofTSH fabrics. The extensive damage of the SgB fabrics diminishescapillarity and therefore the lubricant's ability to redistribute. Thiseffect is not seen on the more durable SiM treatment. SiM Nike PEmaintained the same sliding angle throughout twisting and SgB Nike PEexperienced a continuous increase in sliding angle as the nanostructuresbecame critically damaged. Therefore, with respect to robustness,lubricated SiM-treated fabrics show best performance.

For additional durability characterization, non-lubricated fabricsamples were vigorously rubbed with a Kimwipe, qualitatively observedthe repellency, and characterized the surface with SEM (see FIG. 34).Though the ability to repel water appears to remain unaffected, SEMcharacterization reveals cracking damage on the SgB-treated fabrics andno damage to the SiM-treated fabric (see FIG. 34). Specifically, rubbingcauses the alumina shell to crack and detach from the fiber surface, ina fashion similar to the twisting test. The adhesion of the sol-gelalumina to the fibers was not fully optimized yet to providesufficiently strong damage tolerance against rubbing. In contrast, thesilica microparticles that are covalently attached to the fabric surfaceshow strong adherence between the silica shell and the fiber. ThereforeSiM-treated SLIPS-fabrics maintain omniphobic performance even whensubjected to abrasion. It was also observed that washing machine cycleshave little effect on the integrity of the nanostructures. This furtherdemonstrates that damage to the nanostructures can lead to prematureloss of the lubricant and creation of new pinning points, reducing thefunctional lifetime of the fabric.

Given the results of the twisting and rubbing tests described above,SiM-treated fabrics were selected for Phase III testing. Specifically,M. Cotton, Dense PE, Nike PE, and μfiber were selected to complete thecharacterization of the SLIPS fabrics and show the best overallperformance. Water and hydrocarbon resistance testing was performed toobserve the repellency of low-surface-tension fluids, and drop impacttesting was performed to determine the pressure tolerance of thefabrics, and water vapor transmission testing was performed tocharacterize the fabric's breathability.

For each of the Phase III fabrics, a SLIPS (lubricated) sample wastested against a nonlubricated sample that serves as a representativeTSH control. Liquid droplets of progressively lower surface tension(ranging from 72 mN/m for pure water to 24.0 mN/m for 60% isopropylalcohol) were applied to fabric samples until the test droplet wets thesurface. The scores for the four samples are shown in Table 5.

TABLE 5 AATCC 193 Aqueous Liquid Repellency Score* SiM Treatment -Sample SiM Treatment - dry lubricated M. Cotton 5 5.5 Dense PE 5.5 8Nike PE 4 6.5 μfiber 5 7

Clearly, the lubricated, SLIPS-fabric samples exhibit a higher scorethan their non-lubricated, superhydrophobic counterparts. In otherwords, the presence of the thin lubricating film around the threadsprevents penetration of low-surface-tension liquids that would haveotherwise wet the non-lubricated fabric. The Dense PE achieved themaximum score of 8: 60% IPA in water did not wet the sample and couldslide off without pinning. M. cotton, Nike PE, and μfiber PE werecapable of repelling aqueous liquids down to surface tensions of 26.5,25.0, and 24.5 mN/m, respectively. A particularly interesting trendemerges from these results: the scores for the SLIPS-fabric samplescorrelate with increasingly tight weaves. M. Cotton has the loosestweave and experiences the most pinning; Dense PE has the tightest weaveand thus performs the best. This trend may be attributable to theoverall smoothness of the SLIPS-fabric surface where even sub-millimeterscale roughness can still slightly compromise the ultrasmooth nature oflubricant-infused interface.

To extend the testing to organic liquids, the repellency of the PhaseIII fabrics Were tested against mineral oils and alkanes ofprogressively shorter chain length and lower surface tension. Table 6summarizes the hydrocarbon repellency scores for the Phase III fabricsamples.

TABLE 6 AATCC 118 Hydrocarbon Resistance Score* SiM Treatment - SampleSiM Treatment - dry lubricated M. Cotton 2 5.5 Dense PE 3.5 8 Nike PE 57 μfiber 4.5 6

All test organic droplets pinned to the TSH fabrics and easily slid offof the lubricated, SLIPS-fabric samples. The TSH samples, particularlythe M. Cotton and Dense PE, generally received lower scores than in theaqueous repellency test, indicating that organic liquids with even lowersurface tensions are more prone to infiltrating the spaces within afabric. Despite this, the scores of the lubricated samples in both thehydrocarbon and aqueous tests were within ±1 from each other and followthe same trend of larger weave patterns causing reduced repellency oflow-surface-tension liquids. Again, the dense polyester sample showedrepellency to all of the test liquids and achieved the highest possiblescore of 8. SLIPS-fabric of a sufficiently dense weave can support alubricating film that repels liquid compounds of broad compositions,polarities and surface tensions, which is a remarkable advancement tostain-resistant, fabric-based materials.

In certain embodiments, fabrics having a weave density that exceeds 100,200, 300 and 400 threads/cm³ can be utilized. As used herein, the weavedensity can be calculated by obtaining an SEM image of a fabric,counting the number of threads horizontally across the fabric, within animaged area.

Another important advantage of a lubricated fabric is that it maintainsits slippery, omniphobic performance under pressure. To assess thepressure stability of the Phase III fabric samples, the drop impact testwas carried out using water (surface tension=72.4 mN/m) and tetradecane(surface tension=26.55 mN/m) dropped from a height of 20.4 cm to achievea dynamic pressure shown by the circle markers shown in FIG. 38. Theresults for the drop impact test are shown in FIG. 38: for a liquid of agiven surface tension, the sliding angle is determined immediately afterthe droplet impacts the surface with the shown dynamic pressure. TheSiM-SLIPS Nike PE and Dense PE fabrics retain their liquid repellency athigh pressures (>1500 Pa) while typical lotus-type TSH surfaces fail at400 Pa. The sliding angle of the test liquids on SiM-SLIPS treatedμfiber fabric increases after high impact, however sliding is stillobserved. This indicates that there is a SLIPS layer penetrated by themany protruding fibers on its disordered surface. Sliding angles fornon-lubricated samples are not included because this pressure is abovethe threshold at which the Cassie-to-Wenzel transition occurs; waterdroplets are strongly pinned to the surface and will not slide even fromthe vertical surfaces, while tetradecane droplets simply wet the fabricas expected. SiM-SLIPS Nike PE shows sliding angles below 10° (10 μLdroplet) after a collisional pressure applied by the falling testliquid, while un-lubricated SiM Nike PE shows irreversible pinning inthe same conditions. FIG. 38 shows that liquids of different surfacetensions and dynamic impact pressures do not cause prominent increasesin sliding angle of the SLIPS fabrics. As could be expected based ontightness of fabric weave and surface flatness, the Dense PE and Nike PEboth show the best performance in this test with post-impact slidingangles of 8.8±1.0° and 20.9±2.0°. The fiber showed an increase of ˜10°in sliding angle after impact pressure due to the presence of loosefibers oriented approximately normal to the surface of the fabric. It isworth noting that despite droplet pinning the lubricated fabric wasneither wet nor stained by the test liquid and the pinned droplets couldbe easily washed off the surface leaving no residue.

Breathability, or more specifically, water vapor transmission rate(WVTR), is an important factor in determining suitable applications forSLIPS fabrics. For each experiment, a non-lubricated and a lubricatedsample were tested alongside two controls: a capsule sealed by(impermeable) Parafilm and an open capsule. In all cases, the lubricatedfabric showed a large decrease in breathability relative to thenon-lubricated samples. Table 7 summarizes the WVTR mass change after 24h for the fabrics and PTFE controls.

TABLE 7 WVTR Material Lubrication (g/24 h/m{circumflex over ( )}2 FoldChange No Membrane* Control 947.5 ± 38.7 25.5 Parafilm* Control  37.2 ±18.4 μfiber* None 497.5 ± 61.4 11.1 μfiber* K102 44.6 ± 6.8 Nike PE*None 507.5 ± 70.9 11.5 Nike PE* K102  44.2 ± 15.6 Dense PE* None 270.5 ±36.6 6.1 Dense PE* K102  44.0 ± 22.4 M. Cotton* None 493.3 ± 17.1 3.5 M.Cotton* K102 139.4 ± 17.9 200 nm PTFE* None 473.9 ± 35.8 11.3 200 nmPTFE* K102 42.0 ± 8.0 1 μm PTFE* None 470.9 ± 41.1 14.9 1 μm PTFE* K102 31.6 ± 18.7 20 μm PTFE* None 483.4 ± 49.0 14.1 20 μm PTFE* K102  34.2 ±19.6 Punc. 200 nm PTFE* None 460.5 ± 39.6 3.7 Punc. 200 nm PTFE* K102131.1 ± 76.0

All of the SLIPS samples (lubricated with Krytox 102) except for M.Cotton did not show a statistically significant difference inbreathability from that of the Parafilm control. Non-lubricated μfiber,Nike PE, and Cotton samples exhibit similar breathability despite largedifferences in their relative weave pattern and weave density. Also, theμfiber, Nike PE, and Dense PE all show no breathability (i.e., nodifference from the Parafilm control) while Cotton, the least denselywoven fabric, shows significant (but still low) breathability. Thisintimates the presence of a certain macro-scale pore size thresholdabove which the Krytox does not wick across, leaving a space throughwhich air and water vapor can flow.

While lotus-effect superhydrophobic surfaces have been thoroughlyinvestigated for years and continue to show improvement, their designhas some fundamental shortcomings that will always limit omniphobicity,stain resistance, durability and pressure tolerance. SLIPS overcomethese problems, and nanostructured coatings that achieve the promisingbenefits using readily available fabrics as a substrate have beenengineered. The lubricated structured surfaces display superiorpressure-stable and damage-tolerant repellency to polar and non-polarliquids as compared to TSH surfaces. These lubricatednanostructure-coated fabrics can repel water, oil, dirt and mud;therefore, tents, boots, and other outerwear would be significantlyimproved. In demanding applications in extreme, contaminatedenvironments, where breathability is not the most critical factor, SLIPSfabrics may already provide a unique solution as a stable, anti-foulingmaterial for tactical suits for military, medical gowns and lab coats,specialty garments for construction and manufacturing. SLIPS-fabricconfers pressure-tolerant and damage-tolerant omniphobicity onfabric-based substrates.

Those skilled in the art would readily appreciate that all parametersand configurations described herein are meant to be exemplary and thatactual parameters and configurations will depend upon the specificapplication for which the systems and methods of the present inventionare used. Those skilled in the art will recognize, or be able toascertain using no more than routine experimentation, many equivalentsto the specific embodiments of the invention described herein. It is,therefore, to be understood that the foregoing embodiments are presentedby way of example only and that the invention may be practiced otherwisethan as specifically described. Accordingly, those skilled in the artwould recognize that the examples should not be limited as such. Thepresent invention is directed to each individual feature, system, ormethod described herein. In addition, any combination of two or moresuch features, systems or methods, if such features, systems or methodsare not mutually inconsistent, is included within the scope of thepresent invention.

What is claimed is:
 1. An article having a repellant surface, thearticle comprising: a substrate comprising fabric material having aweave density that is greater than 100 threads/cm²; and a lubricantwetting and adhering to the fabric material to form a stabilized liquidoverlayer, wherein the stabilized liquid overlayer covers the fabricmaterial at a thickness sufficient to form a liquid upper surface abovethe fabric material, wherein the fabric material is functionalized toenhance chemical affinity with the lubricant such that the lubricant issubstantially immobilized over the fabric material to form a repellantsurface.
 2. An article having a repellant inner surface, the articlecomprising: a container comprising an inner surface to contain a complexfluid; a complex fluid having a liquid and one or more other componentswithin said container; and wherein said liquid wets and adheres to theinner surface to form a stabilized liquid overlayer, wherein thestabilized liquid overlayer covers the inner surface at a thicknesssufficient to form a liquid surface on the inner surface, wherein theinner surface and the liquid have an affinity such that the liquid issubstantially immobilized on the inner substrate to form a repellantsurface, the repellant surface repelling other components within saidcomplex fluid.
 3. An optical article having a repellant surface, theoptical article comprising: a substrate comprising transparent ortranslucent material with a surface; a housing that holds the substrate;and a lubricant wetting and adhering to the surface to form a stabilizedliquid overlayer, wherein the stabilized liquid overlayer covers thesurface at a thickness sufficient to form a liquid upper surface abovethe surface, wherein the surface and the lubricant have an affinity foreach other such that the lubricant is substantially immobilized on thesubstrate to form a repellant surface, wherein the housing isinfiltrated with the lubricant to replenish the lubricant onto thesubstrate.
 4. A membrane-like article, the article comprising: amembrane substrate comprising a top surface, a bottom surface, and aplurality of through-holes; a low-surface tension fluid wetting andadhering the top surface, the bottom surface, and inner wallssurrounding the plurality of through-holes, forming a pre-conditioninglayer; and a fluid deposited over the pre-conditioning layer to form aprotective layer, the protective laying providing a repellant surface tothe membrane substrate; wherein the membrane substrate, thepre-conditioning layer, and the protective layer have an affinity toeach other such that the protective layer is substantially immobilizedon the membrane substrate to form the repellant surface.
 5. An articlefor carrying fluid flow, the article comprising: a substrate comprisinga roughened surface; and a lubricant wetting and adhering to theroughened surface to form a stabilized liquid overlayer, wherein thestabilized liquid overlayer covers the roughened surface at a thicknesssufficient to form a liquid upper surface on top of the roughenedsurface, wherein the roughened surface and the lubricant have anaffinity for each other such that the lubricant is substantiallyimmobilized on the substrate to form a slippery surface, the slipperysurface reducing drag and friction of the fluid flow.
 6. A method forprotecting metal or metalized surfaces from corrosion, the methodcomprising: providing a metal or metalized surface; introducingroughness; and chemically functionalizing the metal or metalized surfaceto enhance affinity of the metal surface with a lubricant; andintroducing the lubricant to wet and adhere to the metal or metalizedsurface to form an overlayer; wherein the metal or metalized surface andthe lubricant have an affinity for each other such that the lubricant issubstantially immobilized on the substrate to form a repellant surface,providing anti-corrosion to the metal or metalized surface.
 7. A methodfor protecting surfaces from scaling, the method comprising: providing asurface; introducing roughness; and chemically functionalizing thesurface to enhance affinity of the surface with a lubricant; andintroducing the lubricant to wet and adhere to the surface to form anoverlayer; wherein the surface and the lubricant have an affinity foreach other such that the lubricant is substantially immobilized on thesubstrate to form a repellant surface, providing anti-scaling to themetal surface.
 8. An article having a repellant surface, the articlecomprising: a substrate comprising a roughened surface; a lubricantwetting and adhering to the roughened surface to form a stabilizedliquid overlayer, wherein the liquid covers the roughened surface at athickness sufficient to form a liquid upper surface above the roughenedsurface; and a fragrance enhancer located within said substrate and/orsaid lubricant; wherein the roughened surface and the lubricating liquidhave an affinity for each other such that the lubricating liquid issubstantially immobilized on the substrate to form a repellant surface.9. An article having a repellant surface, the article comprising: asubstrate comprising a plurality of nanostructures embedded in a mediumand having a roughened surface; and a lubricant wetting and adhering tothe roughened surface to form a stabilized liquid overlayer, wherein theliquid covers the roughened surface at a thickness sufficient to form aliquid upper surface above the roughened surface, wherein the roughenedsurface and the lubricating liquid have an affinity for each other suchthat the lubricating liquid is substantially immobilized on thesubstrate to form a repellant surface, wherein the roughened surfaceincludes a microscale or nanoscale structure.
 10. A method forprotecting plastic, glass, ceramic, and composite surfaces fromgraffiti, the method comprising: providing a said solid surface;introducing roughness, chemically functionalizing the said surface toenhance affinity of the said surface with a lubricant; and introducingthe lubricant to wet and adhere to the said surface to form anoverlayer, wherein the said surface and the lubricant have an affinityfor each other such that the lubricant is substantially immobilized onthe substrate to form a repellant surface, providing anti-graffitiproperties to the said surface.
 11. A method for fluid collection, themethod comprising: providing a solid surface; introducing roughness;chemically functionalizing the solid surface to enhance affinity of thesurface with a lubricant; introducing the lubricant to wet and adhere tothe solid surface to form an overlayer, wherein the solid surface andthe lubricant have an affinity for each other such that the lubricant issubstantially immobilized on the substrate to form a repellant surface;condensing condensate droplets on the repellant surface for liquidcollection; and receiving and recovering fluids dispensed in excess in acoating or processing equipment.
 12. An article having a repellantsurface, the article comprising: a substrate comprising a roughenedsurface; and a lubricant wetting and adhering to the roughened surfaceto form a stabilized liquid overlayer, wherein the liquid covers theroughened surface at a thickness sufficient to form a liquid uppersurface above the roughened surface, wherein the roughened surface andthe lubricating liquid have an affinity for each other such that thelubricating liquid is substantially immobilized on the substrate to forma repellant surface, wherein the substrate is a component of a ski, aluge, a surf board, a hovercraft, a winter sports item, or a watersports item, wherein the repellent surface is capable of repelling solidmaterials, fluid materials, or combinations thereof.
 13. A method forprotecting plastic, glass, ceramic, and composite surfaces from scaling,the method comprising: providing a said solid surface; introducingroughness: chemically functionalizing the said surface to enhanceaffinity of the said surface with a lubricant; and introducing thelubricant to wet and adhere to the said surface to form an overlayer,wherein the surface and the lubricant have an affinity for each othersuch that the lubricant is substantially immobilized on the substrate toform a repellant surface, providing anti-scaling to the said surface.14. A method for forming a repellent surface, the method comprising:providing a substrate having a surface; depositing a first materialhaving a charge to said surface; depositing a second material having acharge that is opposite to the charge of the first material;sequentially repeating said depositing a first material and saiddepositing a second material to provide a roughened surface; introducinga lubricant to wet and adhere to said roughened surface to form anoverlayer, wherein said roughened surface and said lubricant have anaffinity for each other such that the lubricant is substantiallyimmobilized on the substrate to form a repellent surface.
 15. The methodof claim 14, further comprising removing said first material or saidsecond material after said sequentially repeating said depositing afirst material and said depositing a second material.